QuickLinks -- Click here to rapidly navigate through this document

EXHIBIT 12

Federal Home Loan Bank of Boston
Computation of Ratio of Earnings to Fixed Charges
(dollars in thousands)

	For the Year Ended December 31,
	2009			2008			2007		2006		2005
Earnings
(Loss) income before assessments	$	(186,751	)	$	(115,826	)	$	269,974	$	266,587	$	177,187
Fixed charges		837,565			2,388,774			3,054,628		2,664,852		1,608,814
Income before assessments and fixed charges		650,814			2,272,948			3,324,602		2,931,439		1,786,001
Fixed Charges
Interest expense		836,262			2,387,497			3,053,401		2,663,585		1,607,602
1/3 of net rent expense(1)		1,303			1,277			1,227		1,267		1,212
Total fixed charges	$	837,565		$	2,388,774		$	3,054,628	$	2,664,852	$	1,608,814
Ratio of earnings to fixed charges		0.78			0.95			1.09		1.10		1.11

(1)

Represents an estimated interest factor.

QuickLinks

EXHIBIT 12

Federal Home Loan Bank of Boston Computation of Ratio of Earnings to Fixed Charges (dollars in thousands)