Prejudgment Interest Calculator

Accurately compute the interest due on a legal award from the cause of action date until the judgment date. This expert prejudgment interest calculator simplifies a complex but crucial financial calculation in litigation.

What is a Prejudgment Interest Calculator?

A prejudgment interest calculator is a specialized financial tool used to determine the amount of interest that has accrued on a sum of money from the time a legal injury occurred until the day a court judgment is made. Prejudgment interest is not a penalty; rather, it is a form of compensation awarded to a plaintiff for the loss of use of money that was rightfully theirs during the litigation period. The core principle is that if the defendant had paid the amount owed at the time of the injury, the plaintiff could have invested or otherwise used those funds. This calculator automates the complex task of computing this interest, which often involves specific start dates, end dates, and varying statutory interest rates.

Prejudgment Interest Formula and Explanation

The most common method for calculating prejudgment interest is the simple interest formula. Compound interest may be allowed in some jurisdictions, but simple interest is the standard. Our prejudgment interest calculator uses this widely accepted approach.

The formula is:

Total Interest = P × R × T

This formula is broken down in practice by the calculator as:

Prejudgment Interest = Principal Amount × (Annual Interest Rate / 100) × (Number of Days / 365)

Formula Variables

Variable	Meaning	Unit	Typical Range
Principal Amount (P)	The base amount of the damages awarded by the court.	Currency (e.g., $, €)	$1,000 – $1,000,000+
Annual Interest Rate (R)	The legal rate of interest set by statute, which varies by jurisdiction.	Percentage (%)	1% – 12%
Time Period (T)	The duration for which interest is calculated, converted to years. Calculated as (End Date – Start Date) / 365.	Years (as a fraction)	0.1 – 10+ years

Practical Examples

Example 1: Personal Injury Case

A plaintiff is awarded $150,000 in a personal injury lawsuit. The cause of action (the accident) occurred on June 1, 2023. The judgment is entered on December 1, 2025. The statutory interest rate in the jurisdiction is 7%.

• Inputs:
  • Principal: $150,000
  • Interest Rate: 7%
  • Start Date: 2023-06-01
  • End Date: 2025-12-01
• Calculation:
  • Number of days: 914
  • Interest = $150,000 * 0.07 * (914 / 365) = $26,301.37
• Result: The prejudgment interest is $26,301.37, making the total judgment $176,301.37.

Example 2: Breach of Contract

A business fails to pay a supplier $45,000 for goods delivered. The payment was due on March 15, 2024. After a lawsuit, a judgment is entered on May 30, 2025. The contract specified an interest rate of 9% on overdue payments.

• Inputs:
  • Principal: $45,000
  • Interest Rate: 9%
  • Start Date: 2024-03-15
  • End Date: 2025-05-30
• Calculation:
  • Number of days: 441
  • Interest = $45,000 * 0.09 * (441 / 365) = $4,905.62
• Result: The prejudgment interest owed is $4,905.62. Use our Breach of Contract Damages Calculator for more scenarios.

How to Use This Prejudgment Interest Calculator

1. Enter the Judgment Principal Amount: Input the base dollar amount awarded by the court, before any interest is added.
2. Provide the Annual Interest Rate: Enter the applicable statutory rate for your jurisdiction. This is a critical factor and can be found in state statutes or by consulting a legal professional. Our Statutory Interest Rates guide can help.
3. Select the Start Date: Choose the date from which interest begins to accrue. This is typically the date the injury or breach occurred.
4. Select the Judgment Date: Choose the date the final judgment was rendered by the court.
5. Review the Results: The calculator will instantly display the total prejudgment interest, the number of days in the period, and the total amount due (principal + interest).

Key Factors That Affect Prejudgment Interest

• Jurisdiction: The single most important factor. Each state or federal jurisdiction has its own laws governing if and how prejudgment interest is awarded.
• Statutory Rate: The interest rate is set by law and can vary from as low as 1% to over 10%. Some states tie it to federal rates.
• Accrual Period: The length of time between the cause of action and the judgment directly impacts the total amount. Longer cases result in more interest.
• Type of Claim: Some jurisdictions have different rules for different types of cases, such as contract disputes, personal injury, or wrongful death. Using the correct Legal Claim Analyzer is crucial.
• Compound vs. Simple Interest: Most jurisdictions use simple interest, but some allow for compounding, which can dramatically increase the award over long periods.
• Settlement Offers: In some states, a reasonable settlement offer rejected by the plaintiff can stop the accrual of prejudgment interest from the date of the offer.

Frequently Asked Questions (FAQ)

1. Is prejudgment interest taxable?

Yes, the interest portion of a legal award is generally considered taxable income by the IRS and must be reported.

2. What’s the difference between prejudgment and post-judgment interest?

Prejudgment interest accrues from the date of injury to the date of judgment. Post-judgment interest accrues from the date of judgment until the date the judgment is paid in full. The Post-Judgment Interest Calculator can compute this for you.

3. Is prejudgment interest always awarded?

No. It depends on the jurisdiction and the type of case. Some statutes make it mandatory, while in other cases it’s at the discretion of the court or jury.

4. Can the interest rate change during the accrual period?

Yes. If the statutory rate changes, you may need to perform separate calculations for each period with a different rate and sum them. This prejudgment interest calculator assumes a single, constant rate for simplicity.

5. Does this calculator handle compound interest?

This calculator uses simple interest, which is the most common method. Compound interest calculations are more complex and less frequently applied in this context.

6. Where do I find the correct interest rate?

The applicable rate is determined by state or federal law. You should consult the statutes for the specific jurisdiction where the case was filed. Consulting with a legal expert is the best way to ensure accuracy.

7. What if the start date is before the end date?

Our prejudgment interest calculator will show an error or zero interest, as interest cannot accrue for a negative time period. The start date must precede the end date.

8. Why is compensating for “loss of use” important?

It’s an issue of economic fairness. The plaintiff was deprived of funds they were entitled to, and prejudgment interest makes them whole by accounting for the time value of that money.