Gera Tools

Prejudgment Interest Calculator

Compute accrued prejudgment interest from damage date to judgment date

Calculates interest on a damages principal from the date of loss or filing to the expected judgment date using a state-specific statutory rate. Commercial litigators and economic-damage experts use it to quantify prejudgment interest for trial. It runs free in your browser on Gera Tools, with nothing uploaded.

Last updated Source: Gera Tools

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.

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.

Worked example

For example, 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 three key inputs that control the award

1. Accrual date

The accrual date is the single most consequential input and the one most often disputed. Depending on jurisdiction and claim type, it may be:

  • Date of injury or breach — when the harm occurred
  • Date the loss became liquidated — when the amount was calculable with reasonable certainty
  • Date the complaint was filed — when litigation commenced
  • Date of demand letter — in some contract disputes

A difference of six months on a large principal can mean tens of thousands of dollars of additional or missing interest. Confirm the controlling rule with counsel before using any figure in expert reports or settlement negotiations.

2. Simple vs compound

Many states mandate simple interest on prejudgment claims. Others permit or require annual compounding. The difference compounds (literally) over long cases:

For illustrative comparison on $250,000 at 6% over three years:

  • Simple: approximately $45,000 in interest
  • Compounded annually: slightly more — the gap grows with rate and time

3. The statutory rate itself

Statutory prejudgment interest rates vary widely by state and some adjust annually (often tied to a US Treasury rate). Using the wrong rate is a common expert error; always verify the current rate against the specific statute for the year the cause of action accrued, as some jurisdictions apply the rate in effect at accrual rather than at the time of trial.

What this calculator does not handle

  • Segmented rates — some jurisdictions apply different rates for different periods (pre-filing vs post-filing, or rates that changed by statute during the litigation)
  • Partial-year conventions — some statutes specify 360-day years for proration; this tool uses 365
  • Offset rules — some states reduce or deny prejudgment interest if the defendant made an offer of judgment or tender that was refused

Use this as a planning estimate and have a damages expert confirm the figure before any filing or expert report.