According to my research, Massachusetts allows 12% post judgment interest. This interest accrues daily from the date of the judgment award to the date of payment.
In most states, post-judgment interest is simple, not compounded. The formula for calculating the interest is:
Judgment (including atty fees and costs) X .12 equals annual interest. Then divide by 365 for daily interest, then multiply times the number of days.
Example: Judgment is $1200, attorney fees are $600, costs are $150.00, days since judgment is 476.
(1200+600+150) X .12 / 365 x 476 = $305.16 interest
As you can see, the longer it takes to pay the judgment in full, the more it will cost you.