What is prejudgment interest?

Prejudgment interest compensates a plaintiff for the time value of money lost between the date the harm occurred (or the suit was filed) and the date of judgment. It is awarded on top of the underlying damages to make the plaintiff whole.

Is prejudgment interest simple or compound?

It depends entirely on the jurisdiction. Many states mandate simple interest at a fixed statutory rate, while others allow annual compounding. This tool lets you choose, but you must confirm the rule for your specific state and claim type.

What rate should I use?

Each state sets its own statutory prejudgment interest rate, and some tie it to a treasury or judgment rate that changes annually. The built-in rates are common defaults; for an actual case, verify the current statutory rate against the controlling statute.

When does interest start accruing?

The accrual date varies by jurisdiction and claim type. It may be the date of the breach or injury, the date the loss became fixed, or the date the complaint was filed. Choosing the wrong start date materially changes the award, so confirm the rule.

Is this a substitute for an expert calculation?

No. Prejudgment interest rules are highly jurisdiction-specific and can involve segmented rates, partial-year proration, and offsets. Use this as a quick estimate and have a damages expert or counsel confirm the figure for trial.

Prejudgment Interest Calculator

Prejudgment interest makes a plaintiff whole for the delay between suffering a loss and recovering a judgment. This calculator applies a state statutory rate to a damages principal over the days from the accrual date to the expected judgment date, supporting both simple and annually compounded methods.

How it works

The day count between accrual and judgment drives the calculation. For simple interest:

total interest = principal × (rate/100) × (days / 365)

For annual compounding the tool compounds whole years and prorates the final partial year:

total = principal × (1 + rate/100) ^ (days / 365) − principal

The result is the accrued interest, plus the principal-and-interest total you can put before the court.

Example and tips

A $250,000 economic loss, accruing at a 6% simple statutory rate over exactly three years (1,095 days), accrues about $45,000 in prejudgment interest, for a total of roughly $295,000. The single most consequential input is the accrual date — confirm whether your jurisdiction runs interest from the date of injury, the date the loss became liquidated, or the filing date, because each can shift the award by months of interest.