Ontario prejudgment interest calculator (PJI)
Free Ontario prejudgment interest calculator for 2026: the published rate is 2.5% for proceedings commenced in Q1–Q3 (Q4 unpublished). This estimate is not legal advice. Estimate simple prejudgment interest using the Courts of Justice Act rate for the quarter when the proceeding started. After the estimate, click Start free — 5 credits and research entitlement and exclusions in the Canadian AI legal research workspace or AI legal research for civil litigation. Then try Curia or see pricing, then start free.
Five free credits. No credit card. Not legal advice. Confirm 2.5% and Q4 status on the 2026 rates guide.
The date the legal reason for the claim arose.
The date the court issued the first document in the case. This selects the applicable quarterly rate.
Interest is estimated through the date the court made the order.
After the worksheet
Research the claim, not just the rate.
An Ontario litigator using this PJI calculator is usually pricing a damages claim. The worksheet estimates simple prejudgment interest from the Courts of Justice Act rate for the quarter when the proceeding started. That arithmetic is the start of the file, not the end of it.
Counsel still has to confirm the principal, damages components, contractual or other statutory rates, exclusions, partial payments, and any variation under sections 128–130. Those issues turn on the authorities — not on a single published percentage.
Curia is an AI legal research workspace for Canadian firms. Open a matter from the Canadian AI legal research workspace, ask the damages or interest question, and review source-linked case law with a transparent citation trail. The calculator stays a public worksheet; the research happens in the workspace. Ontario civil litigators can continue with AI legal research for civil litigation for entitlement, exclusions, and section 130 discretion. Then try Curia or see pricing. Start free — 5 credits. No credit card. Start free.
Calculator questions
Ontario PJI calculator FAQ
What Ontario prejudgment interest rate does this calculator use for 2026?
The worksheet uses the Courts of Justice Act commencement-quarter rate. For 2026, that published prejudgment rate is 2.5% for proceedings commenced in Q1, Q2, or Q3. Q4 is unpublished; the calculator fails closed when a quarter has no published rate. Confirm Ontario's official table or the 2026 rates guide.
Does this PJI calculator apply Rule 53.10 or section 130 discretion?
No. It estimates simple prejudgment interest from the commencement-quarter rate. It does not calculate the 5% Rule 53.10 default for non-pecuniary personal-injury damages, section 128(3) six-month measurement, section 128(4) exclusions, partial payments, or a court's discretion under section 130.
How do I go from a PJI estimate to cited legal research?
Use the estimate as a starting point, then click Start free — 5 credits or Try Curia. Research entitlement, exclusions, and section 130 factors in the Canadian AI legal research workspace against cited case law from the selected province. No credit card.
Related tools and guides
Ontario prejudgment interest guide
CJA sections 128–130, Rule 53.10, published rates, exclusions, partial payments, and section 130 discretion — with primary sources.
Read the guide →AI legal research for civil litigation
Cited case-law research across nine provinces for motions, costs, discovery, evidence, and prejudgment-interest entitlement — then sign up to run it on a file.
Open civil litigation research →Citation checker
Check Ontario and British Columbia case citations against Canadian decision metadata before you rely on them in a damages or interest analysis.
Check citations →AI case assessment
Issue-spot a fictional or redacted Ontario fact pattern, then move the file into a private matter when you are ready for deeper research.
Open assessment →Canadian AI legal research workspace
The product hub for cited research, the matter file, and drafting on one Canadian file — then start free.
Open the workspace →Research across nine provinces
Ask a research question and review cited Canadian case law with source-support indicators and links to the underlying decisions.
See research →Take the interest estimate into a real matter.
Use Curia to research the authorities from your selected province behind the damages claim. Civil files start at AI legal research for civil litigation. Then try Curia or see pricing.
Start free — 5 creditsFive free credits. No credit card.