CALVERT UNCONSTRAINED BOND FUND

Investment Objective

The Fund seeks positive absolute returns over a full market cycle, regardless of market conditions.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for a reduced Class A sales charge if you and your family invest, or agree to invest in the future, at least $50,000 in Calvert mutual funds. Certain financial intermediaries also may offer variations in Fund sales charges to their customers as described in Appendix B – Financial Intermediary Sales Charge Variations.  More information about these and other discounts is available under “Choosing a Share Class” on page 17 and “Reduced Sales Charges” on page 18 of this Prospectus, and under “Method of Distribution” on page 28 of the Fund’s Statement of Additional Information (“SAI”), and from your financial intermediary.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - CALVERT UNCONSTRAINED BOND FUND	CLASS A		CLASS C		CLASS Y	CLASS I
Maximum sales charge (load) on purchases (as a % of offering price)	3.75%		none		none	none
Maximum deferred sales charge (load) (as a % of amount purchased or redeemed, whichever is lower)	none	[1]	1.00%	[2]	none	none

Annual Fund Operating Expenses (expenses that you pay each year as a % of the value of your investment)

Annual Fund Operating Expenses - CALVERT UNCONSTRAINED BOND FUND		CLASS A	CLASS C	CLASS Y	CLASS I
Management fees	[1]	0.47%	0.47%	0.47%	0.47%
Distribution and service (12b-1) fees		0.25%	1.00%	none	none
Other expenses		0.42%	1.80%	0.58%	0.22%
Total annual fund operating expenses		1.14%	3.27%	1.05%	0.69%
Less fee waiver and/or expense reimbursement	[2]	(0.04%)	(1.42%)	(0.20%)	(0.04%)
Total annual fund operating expenses after fee waiver and/or expense reimbursement		1.10%	1.85%	0.85%	0.65%

Example.

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that:

• you invest $10,000 ($1,000,000 in the case of Class I shares) in the Fund for the time periods indicated and then either redeem or hold your shares at the end of those periods;

• your investment has a 5% return each year;

• the Fund's operating expenses remain the same; and

• any expense limitation is in effect for the period indicated in the fee table above.

Although your actual costs may be higher or lower, under these assumptions your costs would be:

Expense Example - CALVERT UNCONSTRAINED BOND FUND - USD ($)	1 Year	3 Years	5 Years	10 Years
CLASS A	483	720	975	1,706
CLASS C	288	874	1,585	3,471
CLASS Y	87	314	560	1,265
CLASS I	6,641	21,669	38,020	85,477

Expense Example, No Redemption - CALVERT UNCONSTRAINED BOND FUND - USD ($)	1 Year	3 Years	5 Years	10 Years
CLASS A	483	720	975	1,706
CLASS C	188	874	1,585	3,471
CLASS Y	87	314	560	1,265
CLASS I	6,641	21,669	38,020	85,477

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (“turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the “Example”, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 104 % of its portfolio’s average value.

Principal Investment Strategies

The Fund seeks to achieve its investment objective through a flexible investment process that allocates investments across global fixed-income markets and uses various investment strategies. The Fund is not constrained by portfolio management relative to an index.

Under normal circumstances, the Fund invests at least 80% of its net assets (including borrowings for investment purposes) in bonds and/or instruments (including derivative instruments) that provide exposure to bonds. Bonds include debt securities of any maturity. The Fund will provide shareholders with at least 60 days’ advance written notice before changing this 80% policy.

The Fund may invest, without limitation, in below-investment grade, high-yield debt securities (commonly known as “junk bonds”), including distressed securities that are in default. The Fund, however, currently does not intend to invest more than 75% of its net assets in such securities. A debt security is considered below investment grade when it is assigned a credit quality rating below BBB- by Standard & Poor’s Ratings Services (“ S&P”) or below Baa3 by Fitch Ratings, Inc. or an equivalent rating by another nationally recognized statistical rating organization (“ NRSRO”), or if unrated, considered to be of comparable credit quality by CRM .

The Fund’s investments may include, but are not limited to the following: bonds issued by U.S. corporations, the U.S. government or its agencies, and U.S. government-sponsored entities (e.g., the Federal National Mortgage Association (“FNMA”) and the Federal Home Loan Mortgage Corporation (“FHLMC”)); debt or debt-related securities issued by foreign governments and corporations; trust preferred securities; taxable municipal securities; asset-backed securities (“ABS”), including commercial mortgage-backed securities; collateralized mortgage obligations (“CMOs”); convertible bonds; investment companies, such as bond exchange-traded funds and closed-end funds; and leveraged loans.

Under normal circumstances, the average portfolio duration of the Fund will vary from negative three (-3) years to positive eight (8) years.  Average portfolio duration will vary depending on the portfolio managers’ outlook on changing market, economic, and political conditions.

The Fund may invest up to 15% of its net assets in equity securities, including preferred and common stock. The Fund may also invest in foreign securities, and up to 50% of the Fund’s net assets may be invested in securities and instruments that are tied to emerging market countries. The Fund may purchase securities denominated in foreign currencies and U.S. dollar-denominated securities of foreign issuers (including depository receipts that evidence ownership in underlying foreign stocks).

The Fund may invest in derivative instruments, such as options, futures contracts (including index futures contracts), currency forwards or swap agreements (including credit default swaps). The use of these derivative transactions may allow the Fund to obtain net long or short exposures to select currencies, interest rates, countries, duration or credit risks. These derivatives may be used to enhance Fund returns, increase liquidity and/or gain exposure to certain instruments or markets (e.g., the corporate bond market) in a more efficient way. In addition, the Fund may invest in “to-be-announced” securities, including when-issued, delayed delivery and forward commitment securities, and may engage in short sales up to 20% of its net assets.

The Fund employs an “absolute return” investment approach. This means that the Fund benchmarks itself to an index of cash instruments, rather than a stock or bond market index, and seeks to achieve returns that exceed its benchmark and are largely independent of broad movements in stocks and bonds. The Fund’s benchmark is the Bloomberg Barclays 1-3 Month U.S. Treasury Bill Index.

Investment decisions for the Fund are made primarily on the basis of fundamental and quantitative research conducted by CRM’s research staff and consideration of the responsible investing criteria described below. Management of the Fund involves consideration of numerous factors (such as quality of business franchises, financial strength, management quality and security structural and collateral considerations). The portfolio managers may sell a security when CRM’s price objective is reached, the fundamentals of the investment change or to pursue more attractive investment options. The portfolio managers intend to focus on risk management and also seek to preserve capital to the extent consistent with the Fund’s investment objectives. The Fund intends to seek to manage investment risk by maintaining broad issuer and industry diversification among its holdings, and by utilizing fundamental analysis of risk/return characteristics in securities selection. The Fund manages duration and any hedging of interest rate risk through the purchase and sale of U.S. Treasury securities and related futures contracts.

Responsible Investing. In selecting investments for the Fund, CRM is guided by The Calvert Principles for Responsible Investment, which provide a framework for considering environmental, social and governance factors that may affect investment performance.

Principal Risks

Bond Market Risk. Economic and other events (whether real, perceived or expected) can reduce the demand for investments held by the Fund, which may reduce their market prices and cause the value of Fund shares to fall. The frequency and magnitude of such changes cannot be predicted. Certain securities and other investments held by the Fund can experience downturns in trading activity and, at such times, the supply of such instruments in the market may exceed the demand. At other times, the demand for such instruments may exceed the supply in the market. An imbalance in supply and demand in the market may result in greater price volatility, less liquidity, wider trading spreads and a lack of price transparency in the market. No active trading market may exist for certain investments, which may impair the ability of the Fund to sell or to realize the full value of such investments in the event of the need to liquidate such assets. Adverse market conditions may impair the liquidity of some actively traded investments. Fixed income markets have recently experienced a period of relatively high volatility due to rising U.S. treasury yields which reflect the market’s expectations for higher U.S. economic growth and inflation. As a result of the Federal Reserve’s recent decision to raise the target fed funds rate following a similar move last year and the possibility that it may continue with such rate increases and/or unwind its quantitative easing program, fixed income markets could experience continuing high volatility, which could negatively impact the Fund’s performance.

Credit Risk. The credit quality of fixed-income securities may deteriorate, which could lead to default or bankruptcy of the issuer where the issuer becomes unable to pay its obligations when due. Such defaults may reduce the value of Fund shares and income distributions.  Changes in economic conditions or other circumstances may reduce the capacity of issuers of a municipal obligation to make principal and interest payments. The value of a municipal obligation also may decline because of real or perceived concerns about the issuer’s ability to make principal and interest payments.

Mortgage-Backed and Asset-Backed Securities Risk. The value of investments in mortgage-backed and asset-backed securities is subject to interest rate risk and credit risk. These securities are also subject to the risk that borrowers will prepay the principal on their loans more quickly than expected (prepayment risk) or more slowly than expected (extension risk), which will affect the yield, average life and price of the securities. In addition, faster than expected prepayments may cause the Fund to invest the prepaid principal in lower yielding securities and slower than expected prepayments may reduce the potential for the Fund to invest in higher yielding securities.

Mortgage-Backed Security Risk (Government-Sponsored Enterprises).  Debt and mortgage-backed securities issued by government-sponsored enterprises (“GSEs”) such as FNMA and FHLMC are neither insured nor guaranteed by the U.S. Treasury and are not backed by the full faith and credit of the U.S. government. Such securities are only supported by the credit of the applicable GSE. The U.S. government has provided financial support to FNMA and FHLMC, but there can be no assurance that it will support these or other GSEs in the future.

Leveraged Loan Risk. Leveraged loans are subject to the risks typically associated with debt securities, such as credit risk discussed above. The loans in which the Fund will invest are expected to be below-investment-grade quality and to bear interest at a floating rate that resets periodically. In addition, leveraged loans, which typically hold a senior position in the capital structure of a borrower, are subject to the risk that a court could subordinate such loans to presently existing or future indebtedness or take other action detrimental to the holders of leveraged loans. Leveraged loans are also subject to the risk that the value of the collateral, if any, securing a loan may decline, be insufficient to meet the obligations of the borrower, or be difficult to liquidate. Some leveraged loans are not as easily purchased or sold as publicly-traded securities and others are illiquid, which may make it more difficult for the Fund to value them or dispose of them at an acceptable price. Leveraged loans are usually more credit sensitive than investment-grade securities.

Management Risk. The individual investments of the Fund may not perform as expected, and the Fund’s portfolio management practices may not achieve the desired result.

Interest Rate Risk. A change in interest rates may adversely affect the value of fixed-income securities. When interest rates rise, the value of fixed-income securities will generally fall. Longer-term securities are subject to greater interest rate risk.

Portfolio Duration Risk. Duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund’s average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Liquidity Risk. Liquidity risk exists when particular investments are difficult to sell. The Fund may be unable to sell illiquid securities at an advantageous time or price or achieve its desired level of exposure to a certain sector. Liquidity risk may result from the lack of an active market, reduced number and capacity of traditional market participants to make a market in fixed-income securities, and may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal, causing increased supply in the market due to selling activity. Illiquid securities also may be difficult to value.

Lower Rated Investment Risk. Investments rated below investment grade and comparable unrated investments (“junk bonds”) can involve a substantial risk of loss. Junk bonds are considered to be speculative with respect to the issuer’s ability to pay interest and principal. These investments also have a higher risk of issuer default, are subject to greater price volatility than investment grade securities and may be illiquid.

Defaulted Bonds Risk. For bonds in default (rated “D” by Standard & Poor’s or the equivalent by another NRSRO), there is a significant risk that these bonds will not achieve their original value.

Unrated Security Risk. Unrated securities may be less liquid than rated securities determined to be of comparable quality. When the Fund purchases unrated securities, it will depend on the investment adviser’s analysis of credit risk without the assessment of an NRSRO.

Corporate and Taxable Municipal Bond Risk. For corporate and taxable municipal bonds, there is credit risk in addition to the interest rate risk that affects all fixed-income securities.

Trust Preferred Securities Risk. Trust preferred securities are preferred stocks issued by a special purpose trust subsidiary backed by subordinated debt of the corporate parent. Trust preferred securities are subject to unique risks, which include the fact that dividend payments will only be paid if interest payments on the underlying obligations are made, which interest payments are dependent on the financial condition of the parent corporation. There is also the risk that the underlying obligations, and thus the trust preferred securities, may be prepaid after a stated call date or as a result of certain tax or regulatory events, resulting in a lower yield to maturity. There can be no assurance as to the liquidity of trust preferred securities and the ability of holders of such securities to sell their holdings.

Collateralized Mortgage Obligation and Structured Asset-Backed Securities Risk. A CMO is a multiclass bond that is backed by a pool of mortgage loans or mortgage-backed securities. A structured ABS is a multiclass bond that is typically backed by a pool of auto loans, credit card receivables, home equity loans or student loans. A CMO or structured ABS is subject to interest rate risk, credit risk, prepayment risk and extension risk. In addition, if the Fund holds a class of a CMO or a structured ABS that is subordinated to other classes backed by the same pool of collateral, the likelihood that the Fund will receive payments of principal may be substantially limited.

Foreign Securities Risk. Investing in foreign securities involves additional risks relating to political, social, and economic developments abroad. Other risks result from the differences between the regulations to which U.S. and foreign issuers and markets are subject, and the potential for foreign markets to be less liquid and more volatile than U.S. markets. Foreign securities include ADRs. Unsponsored ADRs involve additional risks because U.S. reporting requirements do not apply and the issuing bank will recover shareholder distribution costs from movement of share prices and payment of dividends.

Emerging Markets Risk. The risks of investing in emerging market securities are greater than those of investing in securities of developed foreign countries. These risks include volatile currency exchange rates, periods of high inflation, increased risk of default, greater social, economic and political uncertainty and instability, less governmental supervision and regulation of securities markets, weaker auditing and financial reporting standards, lack of liquidity in the markets, and the significantly smaller market capitalizations of emerging market issuers.

Foreign Currency Risk. Securities that trade or are denominated in currencies other than the U.S. dollar may be adversely affected by fluctuations in currency exchange rates. When the U.S. dollar strengthens relative to a foreign currency, the U.S. dollar value of an investment denominated in that currency will typically fall. ADRs indirectly bear currency risk because they represent an interest in securities that are not denominated in U.S. dollars.

Investment in Other Investment Companies Risk. The Fund may invest in securities of other investment companies, such as open-end or closed-end management investment companies, including exchange-traded funds. The Fund may invest in other investment companies to gain broad market or sector exposure, including during periods when it has large amounts of uninvested cash or when the Adviser believes share prices of other investment companies offer attractive values. As a shareholder of an investment company, the Fund may indirectly bear investment advisory fees, supervisory and administrative fees, service fees and other fees which are in addition to the fees the Fund pays its service providers.

Convertible Securities Risk. The values of the convertible securities in which the Fund may invest will be affected by market interest rates, the risk that the issuer may default on interest or principal payments and the value of the underlying common stock into which these securities may be converted. Specifically, certain types of convertible securities may pay fixed interest and dividends, and their values may fall if market interest rates rise and rise if market interest rates fall. Additionally, an issuer may have the right to buy back certain of the convertible securities at a time that is unfavorable to the Fund.

Stock Market Risk. The market prices of stocks held by the Fund may fall.

Common Stock Risk. Although common stocks have a history of long-term growth in value, their prices fluctuate based on changes in a company’s financial condition, on overall market and economic conditions, and on investors’ perception of a company’s well-being.

Preferred Stock Risk. The market value of preferred stock generally decreases when interest rates rise and is affected by the issuer’s ability to make payments on the preferred stock.

Derivatives Risk. Derivatives are investments whose value depends on (or is derived from) the value of an underlying instrument, such as a security, asset, reference rate or index. Derivative strategies often involve leverage, which may exaggerate a loss, potentially causing the Fund to lose more money than it would have lost had it invested in the underlying instrument. Derivatives may be difficult to sell, unwind or value. Derivatives may also be subject to counterparty risk, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable to honor its contractual obligations to the Fund. Swap transactions tend to shift the Fund’s investment exposure from one type of investment to another, and therefore entail the risk that a party will default on its payment obligations to the Fund. Futures may be more volatile than direct investments in the instrument underlying the futures, and may not correlate perfectly to the underlying instrument. Futures also may involve a small initial investment relative to the risk assumed, which could result in losses greater than if they had not been used. Due to fluctuations in the price of the underlying security, the Fund may not be able to profitably exercise an option and may lose its entire investment in an option. Forward commitments entail the risk that the instrument may be worth less when it is issued or received than the price the Fund agreed to pay when it made the commitment. The use of foreign currency forwards may result in currency exchange losses due to fluctuations in currency exchange rates or an imperfect correlation between portfolio holdings denominated in a particular currency and the forward contracts entered into by the Fund.

To-Be-Announced (“TBA”) Securities Risk. In a TBA securities transaction, the Fund commits to purchase certain securities for a fixed price at a future date.  TBA securities include when-issued and delayed delivery securities and forward commitments. TBA securities involve the risk that the security the Fund buys will lose value prior to its delivery. There also is the risk that the security will not be issued or that the other party to the transaction will not meet its obligation. If this occurs, the Fund loses both the investment opportunity for the assets it set aside to pay for the security and any gain in the security’s price.

Short Sale Risk. Positions in shorted securities are speculative and more risky than long positions. Such investments involve the potential loss of more money than the actual cost of the investment, and the risk that the third party to the short sale may fail to honor its contract terms, causing a loss to the Fund.  Short sale strategies are often categorized as a form of leveraging or speculative investment. The use of leverage may multiply small price movements in securities into large changes in value. As a result of using leverage, the Fund’s share price may be more volatile than if no leverage were used.

Active Trading Strategy Risk. The Fund employs an active style that seeks to position the Fund with securities that offer the greatest price appreciation while minimizing risk. This style can result in higher turnover (exceeding 100%), may translate to higher transaction costs and may increase your tax liability.

Responsible Investing Risk. Investing primarily in responsible investments carries the risk that, under certain market conditions, the Fund may underperform funds that do not utilize a responsible investment strategy.  The application of responsible investment criteria may affect the Fund’s exposure to certain sectors or types of investments, and may impact the Fund’s relative investment performance depending on whether such sectors or investments are in or out of favor in the market.  An investment’s environmental, social and governance (“ESG”) performance, or the Adviser’s assessment of such performance, may change over time, which could cause the Fund to temporarily hold investments that do not comply with the Fund’s responsible investment criteria.  In evaluating an investment, the Adviser is dependent upon information and data that may be incomplete, inaccurate or unavailable, which could cause the Adviser to misanalyze the ESG factors relevant to a particular investment.  Successful application of the Fund’s responsible investment strategy will depend on the Adviser’s skill in properly identifying and analyzing material ESG issues.

General Fund Investing Risks. The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objective. It is possible to lose money by investing in the Fund. The Fund is designed to be a long-term investment vehicle and is not suited for short-term trading. Investors in the Fund should have a long-term investment perspective and be able to tolerate potentially sharp declines in value. An investment in the Fund is not a deposit in a bank and is not insured.

Performance

The following bar chart and table provide some indication of the risks of investing in the Fund by showing how the Fund’s average annual returns over time compare with those of a broad-based securities market index. The return in the bar chart is for Class A shares and does not reflect a sales charge. If the sales charge was reflected, the return would be lower. Past performance (both before and after taxes) is no guarantee of future results.

Effective December 31, 2016, Calvert Research and Management (“CRM”) is the investment adviser to the Fund and performance reflected prior to such date is that of the Fund’s former investment adviser, Calvert Investment Management, Inc.  Performance for all periods has been calculated by CRM, the Portfolio’s current administrator, in accordance with applicable requirements.   The Fund’s performance reflects the effects of expense reductions. Absent these reductions, performance would have been lower. Updated Fund performance information can be obtained by visiting www.calvert.com.

During the period from December 31, 2014 through December 31, 2016 , the highest quarterly total return for Class A was 2.42 % for the quarter ended June 30, 2016 and the lowest quarterly return was -0.89% for the quarter ended September 30, 2015.

Average Annual Total Returns as of December 31, 2016

Average Annual Total Returns - CALVERT UNCONSTRAINED BOND FUND	Label	One Year	Life of Fund
CLASS A	Return Before Taxes	2.23%	1.70%
CLASS A | After Taxes on Distributions	Return After Taxes on Distributions	0.45%	0.33%
CLASS A | After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Class A Shares	1.24%	0.66%
CLASS C	Return Before Taxes	4.45%	2.66%
CLASS Y	Return Before Taxes	6.73%	3.87%
CLASS I	Return Before Taxes	6.51%	3.65%
Bloomberg Barclays 1-3 Month U.S. Treasury Bill Index (reflects no deduction for fees, expenses or taxes)	Bloomberg Barclays 1-3 Month U.S. Treasury Bill Index (reflects no deduction for fees, expenses or taxes)	0.26%	0.13%

These returns reflect the maximum sales charge for Class A (3.75%) and any applicable contingent deferred sales charge (“CDSC”) for Class C. Investors cannot invest directly in an Index.

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. The after-tax returns shown are not relevant to you if you hold your Fund shares through a tax-deferred arrangement such as a 401(k) plan or individual retirement account. The return after taxes on distributions and sale of Fund shares may be higher than the return before taxes because the calculation assumes that shareholders receive a tax benefit for capital losses incurred on the sale of their shares. After-tax returns are shown only for Class A shares; after-tax returns for other Classes will vary.

[1] Purchases of Class A shares at net asset value for accounts with $1,000,000 or more on which a finder's fee has been paid are subject to a one-year contingent deferred sales charge of 0.80%.

[2] Applies to redemptions of Class C shares within one year of purchase.

[1] Management fees are restated to reflect current contractual fees rather than the fees paid during the previous fiscal year.

[2] Calvert Research and Management ("CRM") has agreed to reimburse the Fund's expenses to the extent that Total Annual Fund Operating Expenses exceed 1.10% for Class A shares, 1.85% for Class C shares, 0.85% for Class Y shares and 0.65% for Class I shares . This expense reimbursement will continue through April 30, 2018. Any amendment to or termination of this reimbursement would require approval of the Board of Trustees. The expense reimbursement relates to ordinary operating expenses only and does not include expenses such as: brokerage commissions, acquired fund fees and expenses of unaffiliated funds, interest expense, taxes or litigation expenses. Amounts reimbursed may be recouped by CRM during the same fiscal year to the extent actual expenses are less than the contractual expense cap during such year. The contractual administrative fee is 0.12%. CRM has agreed to contractually waive 0.02% of the administrative fee on Class I shares through April 30, 2018.