How statutory interest on an unpaid debt is calculated
There is no single national interest rate for overdue debts in the United States. Each state fixes its own legal rate, and it often differs for contracts, judgments and consumer debts. Enter the principal, the date the debt came due, an end date and the rate that applies, and this tool shows the days accrued, the daily interest, the interest total and the balance including principal.
California sets post-judgment interest at 10% in Cal. Civ. Proc. Code §685.010, while New York uses 9% under CPLR §5004 with a 2% rate for consumer debt judgments. Judgments in federal court instead accrue interest under 28 U.S.C. §1961 at a rate tied to Treasury yields and published weekly. Because these figures change by statute and by case type, the rate field is left blank rather than defaulted. Rates described are those in force as of September 2026. Days are counted from the day after the debt became due through the end date, and interest is prorated on a 365-day year.
Whether interest runs before judgment at all, and from which date, is itself a matter of state law and sometimes of the court's discretion. This calculator is for reference only and is not legal advice. Consult a licensed attorney about your specific situation.
Frequently asked questions
No. Many states use one rate for the period before judgment and a different one after, and the post-judgment rate is usually the one fixed by statute.
Usually yes, up to the limit set by the state's usury law. The statutory legal rate fills the gap when the agreement is silent or the agreed rate is unenforceable.