Sometimes the simplest tools can be the most useful. This is a link to a free post-judgment interest calculator:
http://www.nationaljudgment.net/intcalc.htm . While designed as a post-judgment interest calculator, it can be utilized to calculate the interest on any debt by merely inserting the date the debt was incurred and the interest rate applicable and hitting the calculate button. I use this tool almost daily to calculate interest on judgments to provide debtors with a complete payoff. Post-judgment interest should never be ignored as an important tool to maximize the value of the debt collected. Post-judgment interest can also be a valuable negotiation tool if you are looking for a bargaining chip to give up to a debtor. A debtor who has to pay the full amount of the principal of the debt, filing fees, service of process fees and attorney's fees will feel vindicated if you can give him an exact dollar and cents figure for the amount of post-judgment interest that you are agreeing to waive in exchange for immediate full payment.