Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2023

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

We calculated the fair value of stock options on the date of grant using the Black-Scholes-Merton model and the assumptions listed below:

	January 2022 Grant			January 2021 Grant			March 2020 Grant
Grant date price per share of stock   option award	$	32.19		$	29.84		$	19.63
Expected dividend yield per share		0.00	%		0.00	%		0.00	%
Expected life in years		6.76			6.64			6.40
Expected volatility		54.50	%		54.80	%		42.85	%
Risk-free interest rate		1.52	%		0.59	%		0.87	%
Grant date fair value per share of option   awards	$	17.58		$	15.79		$	8.42

Summary of Performance Stock Units

The following table shows a summary of the performance stock units as of June 30, 2023:

Performance Period	Minimum Shares		Target Shares		Maximum Shares
Market Condition Units
2021 – 2023		66,968		115,036		163,104
2022 – 2024		17,788		117,937		218,086
2023 – 2025		0		78,411		156,822
Performance Condition Units
2023 – 2025		0		188,238		376,476

Summary of Status and Activity of Non-Vested Stock Units

The following table shows a summary of the status and activity of non-vested stock units:

	Restricted Stock Units			Performance Stock Units			Total Stock Units			Weighted Average Grant Date Fair Value per Unit
Non-vested at December 31, 2022		524,612			237,032			761,644		$	32.40
Granted		232,494			267,073			499,567		$	30.75
Credited from dividends		3,469			1,594			5,063		$	26.89
Vested		(216,257	)		0			(216,257	)	$	26.30
Forfeited		(13,609	)		(6,077	)		(19,686	)	$	32.50
Non-vested at June 30, 2023		530,709			499,622			1,030,331		$	32.85

Summary of Status and Activity of Stock Options

The following table shows a summary of the status and activity of stock options:

	Options			Weighted Average Exercise Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2022		1,122,136		$	27.05
Exercised		(63,974	)	$	18.76
Expired		(50,031	)	$	42.16
Outstanding at June 30, 2023		1,008,131		$	26.83		4.55	$	9.0
Exercisable at June 30, 2023		846,655		$	26.56		3.94	$	8.1

Schedule of Stock-based Compensation Expense Recognized

The following table presents total stock-based compensation expense recognized under our LTIP and employee stock purchase plan:

	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
(Dollars in millions)
Stock-based compensation expense recognized:
Selling, general and administrative expenses	$	3.8	$	3.2	$	7.8	$	6.7
Less related income tax benefit		1.1		1.1		2.2		2.3
Decrease in net income attributable to Koppers	$	2.7	$	2.1	$	5.6	$	4.4
Intrinsic value of exercised stock options	$	0.2	$	0.0	$	0.9	$	0.0
Cash received from the exercise of stock options	$	0.3	$	0.0	$	1.2	$	0.0

Performance Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Options And Performance Award Fair Value Assumptions

We calculated the fair value of the performance stock unit awards with a market condition on the date of grant using the assumptions listed below:

	January 2023 Grant			January 2022 Grant			January 2021 Grant
Grant date price per share of performance   award	$	29.01		$	32.19		$	29.84
Expected volatility		66.30	%		66.90	%		68.70	%
Risk-free interest rate		4.11	%		1.10	%		0.16	%
Look-back period in years		3.00			3.00			3.00
Grant date fair value per share	$	39.51		$	45.19		$	41.50