To calculate post-judgment interest, one must first ascertain certain things. First of all, does the judgment allow for interest accumulation? Secondly, what is the designated rate of interest? Lastly, how often is interest accrued and is it compounded? Once these things are known, one can calculate interest using a simple interest calculator, similar to those used to calculate the interest
. on a loan. One simply uses the day of the judgment as the starting point.