Rule 3.01 day counting with rule-cited presets for the Defence, Defendant's Claim, six-month service, settlement conference disclosure, motion notice, motion filing, responding affidavit and witness summons, plus custom modes.

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Defendant's Claim / Counterclaim Estimator

Compare gross claims, model deadlines, and check the jurisdiction flag.

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Which calculator should I use?

Pick the task you are actually doing. Each entry says what the calculator works out and one thing it deliberately does not decide for you.

Working out interest

Ontario Court Interest Calculator
Calculates: prejudgment or postjudgment simple interest across quarterly rate periods, with payments applied in the order you choose and a day-by-day ledger.
Does not decide: whether interest is payable at all, or the date the cause of action arose - the court decides both, and section 130 of the Courts of Justice Act lets it vary or refuse interest.

Landlord and tenant amounts

Rent Arrears Calculator
Calculates: the running balance of rent charged, daily compensation after a tenancy ends, payments received and any deposit credit you apply.
Does not decide: whether the Landlord and Tenant Board will order eviction or the amount it will order - that is the Board's decision on the evidence.
Rent Increase Calculator
Calculates: the guideline increase amount, the earliest lawful effective date under the 12-month rule and the 90-day notice date.
Does not decide: whether the unit is exempt from the guideline, or whether an above-guideline increase would be approved.

Invoices and tax

Legal Fees and HST Calculator
Calculates: fees, taxable and non-taxable disbursements, HST at 13% and any retainer credit, split the way CRA agency principles treat each line.
Does not decide: whether a particular disbursement genuinely qualifies as an agency payment for your file, or whether a fee is reasonable under Law Society rules.

Starting or responding to a Small Claims Court case

Claim Value Estimator
Calculates: net principal plus interest and recoverable amounts, and flags whether the total sits above the $50,000 monetary jurisdiction.
Does not decide: whether your claim is legally sound, or whether abandoning the excess to stay under the limit is the right strategic choice.
Defendant's Claim / Counterclaim Estimator
Calculates: the gross exposure on both sides and the net position if both claims succeeded as pleaded.
Does not decide: whether the person you want to add can properly be claimed against under Rule 10.01(1), or whether leave would be granted late.

Court fees and costs

Court Fee Calculator
Calculates: the clerk's fees payable at each step under O. Reg. 332/16, at the infrequent or frequent claimant rate.
Does not decide: whether you qualify for a fee waiver, or what an enforcement office or sheriff will charge in disbursements.
Costs Estimator
Calculates: a party-and-party costs model tested against the 15% cap in section 29 of the Courts of Justice Act.
Does not decide: what costs a judge will actually award - costs are discretionary, and the cap is a ceiling, not an entitlement.

Deadlines

Ontario Small Claims Court Deadline Calculator
Calculates: a date under the Rule 3.01 counting and holiday rules, from rule-cited presets or a custom day count, counting forward from an event or backward to plan for one.
Does not decide: when service is deemed effective on your facts, or whether the court would extend or abridge the time under Rule 3.02.

Enforcing a judgment

Wage and Bank Garnishment Estimator
Calculates: the amount potentially attachable using the Wages Act 20% default on wages, the joint-account share on bank funds, and the notice fee shown separately.
Does not decide: whether the court will vary the exemption under the Wages Act, or whether the funds are exempt for another reason.

How these calculators work

Shared method. Every calculator on this site is deterministic. The same inputs always produce the same outputs, because each one runs a fixed arithmetic model with published constants - the Ontario prejudgment and postjudgment interest rates, the O. Reg. 332/16 fee amounts, the 13% Ontario HST rate, the section 29 costs cap, the Wages Act garnishment percentages and the rent increase guideline. Nothing is estimated by a model that guesses, and nothing changes between visits unless we publish a constants update.

Privacy. Calculations run entirely in your browser. The amounts, dates and names you type are not sent to a server, not stored in a database, and not shared with anyone. Closing the tab discards them.

Estimate status. Results are estimates for planning and discussion. They are not legal advice, not a court order, not a tribunal calculation and not a bill. A judge, deputy judge, adjudicator, clerk or assessment officer can reach a different figure on the same facts, and often will where the law gives them discretion.

Sources and review. Each calculator lists the statute, regulation or official Ontario page behind its numbers, and shows the date the constants were last reviewed. When a rate or fee changes, the constant and the review date change together.

How to verify a result. Open the source links on the calculator page and confirm the rate, fee or percentage still matches. Then re-run the arithmetic on the shown breakdown: every calculator exposes its intermediate steps so you can check each line rather than trusting one total. If a figure looks wrong, tell us through the Feedback and Corrections form.