Judgment interest calculator

Calculate interest, total payoff, elapsed days, and the starting daily per-diem at a rate you have already verified. Choose simple interest or annual compounding and make the end-date convention explicit.

This tool does not choose the legal rate. Find the recorded rate and rule in the state judgment-interest directory, or use the dedicated federal §1961 calculator. Confirm the controlling official source, effective date, compounding rule, and claim-specific exceptions before entering it.

This calculator performs arithmetic only. It does not determine the governing rate, whether interest is available, the proper start date, payment allocation, or court-specific rounding. Confirm those inputs against the controlling source before relying on the result.

How the judgment interest calculation works

For simple interest, the arithmetic is:

interest = principal × annual rate × accrual days ÷ 365

The per diem is the one-day version of that formula: principal × annual rate ÷ 365. Annual compounding uses the same daily accrual during each year, then adds accrued interest to the balance on the anniversary so the next year starts with a larger base.

Inputs to verify before relying on a payoff

Governing rate: use the rate in force for the correct jurisdiction, judgment date, claim type, and amount. Do not assume today’s rate applies to an older judgment.
Accrual date: identify when interest legally begins—not merely when a loss, invoice, verdict, or demand occurred.
Simple or compound: the statute or judgment controls. Federal post-judgment interest compounds annually; many state judgment rates are simple, but exceptions exist.
End-date treatment: payoff instructions and courts can count dates differently. Use the checkbox to test either convention and retain the convention in the copied result.

What requires a more detailed calculation

This fixed-rate tool intentionally does not model partial payments, fees that do not earn interest, changing statutory rates, tiered rates, leap-year day-count rules, amended judgments, or different rules before and after judgment. Those facts require a period-by-period ledger. Use the recorded state rate pages to identify changes and verify the method against the controlling source.

Frequently asked questions

What rate should I enter in a judgment interest calculator?

Enter the rate required by the controlling judgment, statute, or court rule for the relevant date and claim type. State rules vary, and federal judgments use the separate 28 U.S.C. §1961 method. StatuteRates provides cited state rate pages, but you should confirm the official source before calculating.

What is the per-diem interest on a judgment?

The starting per diem shown here is the judgment amount multiplied by the annual rate, divided by 365. With annual compounding, the daily amount rises after accrued interest is added to the balance on an anniversary.

Should the payoff date count as an interest-accruing day?

Court and payoff conventions differ. The calculator lets you include or exclude the payoff date and states the choice in the result. Confirm the convention required by the governing court or payoff instructions.

Can this calculator handle rate changes or partial payments?

No. It applies one fixed annual rate to one principal amount. A judgment with changing rates, partial payments, fees, non-interest-bearing costs, or claim-specific branches requires a segmented calculation under the controlling rules.

Reference arithmetic only—not legal, tax, or financial advice. A correct calculation depends on correct legal inputs. Confirm the rate, principal, dates, day-count convention, compounding, and payment allocation against the controlling judgment, statute, and court practice.