Calculate prejudgment interest under section 128 of the Courts of Justice Act. Enter your dates and the calculator selects the correct quarterly rate automatically — then computes the simple interest owing. Updated for 2026.
· Reviewed by Jonathan Kleiman, J.D.
Prejudgment interest is calculated under section 128 of the Courts of Justice Act using the quarterly rate published by the Ontario Ministry of the Attorney General. Enter the date your claim was issued and the calculator picks the right rate for you. The current prejudgment rate (Q2 2026) is 2.5%.
Enter your claim details below. Fields marked with * are required.
Prejudgment interest compensates you for being kept out of your money between the date your cause of action arose and the date the court makes its order. It is governed by section 128 of the Courts of Justice Act and calculated as simple interest at the rate published quarterly by the Ministry of the Attorney General.
Interest = Principal × Rate × Days ÷ 365
Where Rate is the prejudgment rate for the quarter the proceeding was commenced, and Days is the number of days from the date the cause of action arose to the date of the order. This mirrors the day-count method on the court's own Form 19D (default judgment).
This is the detail most people get wrong. The rate is fixed by the quarter in which the proceeding was commenced — the date the claim was issued by the court — not the quarter when the cause of action arose, and not the rate in effect at the date of judgment. Once set, that single rate applies across the entire prejudgment period.
| Quarter | Prejudgment Rate | Postjudgment Rate |
|---|---|---|
| Q2 2026 (Apr – Jun) | 2.5% | 4.0% |
| Q1 2026 (Jan – Mar) | 2.5% | 4.0% |
| Q4 2025 (Oct – Dec) | 3.0% | 4.0% |
| Q3 2025 (Jul – Sep) | 3.0% | 4.0% |
| Q2 2025 (Apr – Jun) | 3.3% | 5.0% |
| Q1 2025 (Jan – Mar) | 4.0% | 5.0% |
| Q4 2024 (Oct – Dec) | 4.8% | 6.0% |
| Q3 2024 (Jul – Sep) | 5.3% | 7.0% |
| Q2 2024 (Apr – Jun) | 5.3% | 7.0% |
| Q1 2024 (Jan – Mar) | 5.3% | 7.0% |
| Q4 2023 (Oct – Dec) | 5.3% | 7.0% |
| Q3 2023 (Jul – Sep) | 4.8% | 6.0% |
Source: Ontario Ministry of the Attorney General. The calculator stores the full official series back to 2000.
Section 128(4) carves out several categories. Prejudgment interest is generally not available on:
Personal injury — the 5% rule. In a personal injury action, interest on non-pecuniary (pain and suffering) damages is fixed at 5% per year under Rule 53.10 — not the quarterly table rate. The Court of Appeal confirmed 5% as the presumptive default in 2024. Use the rate override field if you are calculating that head of damages.
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Prejudgment interest covers the period before judgment — from when your claim arose to the date of the order. Postjudgment interest covers the period after, accruing on the amount of the order until it is paid, at a different (higher) rate set by the quarter the order was made. If you already have a judgment, use the Ontario Postjudgment Interest Calculator instead.
Pursuing a smaller debt? The Small Claims Court Calculator rolls interest, court fees, and recoverable costs into a single estimate of what your claim is worth.
Prejudgment interest compensates a successful party for being out of pocket between the date their cause of action arose and the date the court makes its order. It is awarded under section 128 of the Courts of Justice Act at the quarterly rate set by the Ministry of the Attorney General, calculated as simple interest.
For Q2 2026 (April – June), the Ontario prejudgment interest rate is 2.5%. The rate that applies to your case is the rate for the quarter in which your proceeding was commenced (when the claim was issued), and that rate stays fixed for the whole prejudgment period — it does not change quarter to quarter.
The rate is set by the quarter the proceeding was commenced — when the claim was issued by the court — not the quarter when the cause of action arose. Interest still runs from the date the cause of action arose, but the rate itself is locked by the commencement date. That is why this calculator asks for both dates.
It is simple interest by default — it does not accrue interest on itself. Compound interest is only available where a contract pleaded in the claim provides for it, or in the limited circumstances where a court exercises its discretion under s. 130.
No. Under s. 128(4), prejudgment interest is not awarded on punitive or exemplary damages, on interest itself, on costs, or on the part of an award representing pecuniary loss that arises after the order. In a personal injury action, non-pecuniary damages carry a fixed 5% rate under Rule 53.10 rather than the quarterly table rate.
Yes. The Small Claims Court is a branch of the Superior Court of Justice, so s. 128 applies the same way. Remember to claim interest in your Plaintiff's Claim. For a full claim estimate including court fees and recoverable costs, use the Small Claims Court Calculator.
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