How Loan Interest Is Calculated in Canada

Interest is the rent you pay on borrowed money. In Canada, it is calculated on the balance you still owe, at a rate quoted per year and applied over the time you actually hold the money. That is the whole engine. Everything else — how often interest is compounded, whether the rate is fixed or variable, how long you stretch the repayment — changes how much interest the engine produces, not how it works.

One thing to clear up before we go further: LoanGoose is a loan matching and comparison service, not a lender. We do not set rates, make credit decisions, or approve anyone. What we can do is explain the arithmetic so an offer reads like plain English.

The basic calculation

Start with simple interest: interest = balance × rate × time. Owe less, or owe it for a shorter stretch, and you pay less. A lower rate does the same. Three levers, nothing mystical.

Real loans add one wrinkle: the balance moves. Each payment covers the interest that has built up since your last payment, and whatever is left over reduces the principal. Next period, interest is charged on that smaller balance. This is why early payments on a long loan feel like they barely touch the amount you borrowed — most of each payment is rent rather than repayment. Over time, the split flips.

Time is the part people get wrong. Rates are quoted annually, but interest is normally worked out for the lender's chosen period and then added to the balance. How often that happens is set out in your agreement, and it matters, because the more often interest is added, the more interest the following period charges.

Rate versus total cost of borrowing

The headline rate is not the bill. The bill is the total cost of borrowing — interest plus the fees and charges the agreement includes, added up over the life of the loan. Two offers at the same rate can carry very different totals if one has an origination fee, an administration fee, or an early-payout penalty.

So ask for the total in dollars. Then ask two more questions: what happens if you pay the loan off early, and what happens if a payment is late. Prepayment penalties and late charges are where a cheap-looking loan turns expensive. The Financial Consumer Agency of Canada's pages on FCAC — personal loans are a reasonable starting point for the questions worth putting to a lender.

Compounding: why mortgages get their own rule

Not every product compounds the same way. Canadian fixed-rate mortgages are compounded semi-annually by law — a legal convention, not a lender's preference — which is why the same quoted percentage can produce a slightly different effective annual cost on a mortgage than on a loan that compounds on another schedule. The FCAC — mortgages material walks through how that shows up in an amortization schedule.

Variable-rate products behave differently again. The rate itself moves, usually in response to decisions at the Bank of Canada, so either your payment or your amortization adjusts. Bank of Canada — rates publishes the policy rate if you want to follow the trail yourself.

What actually moves your total interest

Most of the variation between two borrowers comes down to a short list. Here is how each item affects the arithmetic.

How a lender decides what rate to offer you

Your rate is a risk price. Lenders look at your credit history, your income stability, the debts you already carry, and how much of your income a new payment would consume. Canada has two national credit reporting bureaus — Equifax Canada and TransUnion Canada — and you can get a free copy of your credit report from each. The FCAC — credit reports and scores page explains what sits in those files and how to correct errors, which is worth doing before you apply anywhere.

For mortgages, federally regulated lenders generally work to a total debt service ratio ceiling of about 44% and apply a qualifying stress-test rate above the contract rate, as set out in OSFI Guideline B-20 — residential mortgage underwriting. In plain terms, you qualify at a higher rate than the one you sign at. At federally regulated lenders, a home equity line of credit is generally limited to 65% of appraised property value, with total secured lending usually capped at 80%.

Payday loans and short-term credit

A payday loan is generally up to $1,500 for a term of 62 days or less. Where a province operates a licensed payday lending regime, federal regulations cap the cost of borrowing at $14 per $100 advanced; a province can set a lower cap, and the lower figure applies. You can read the rule itself in the Payday Lending Regulations, SOR/2024-114, and the FCAC — payday loans page for how licensing works province by province.

Quebec is worth noting: it does not license payday lending, which effectively prohibits the model there. And the Criminal Code sets the criminal rate of interest at 35% per year, in force since 2025-01-01 and calculated by a defined method that aggregates interest and certain charges — see Criminal Code s. 347 — criminal rate of interest. Anything above that line is a criminal offence, not a pricing strategy.

The uncomfortable arithmetic with very short loans is this: a charge that looks small over two weeks is charged again if you renew, and again after that. Stretched across a year, the cost climbs far past anything an instalment loan would charge. If the gap you are covering will reappear next month, the loan is not the fix. It is a new cost added to an old problem.

Questions to ask before you sign

1. What is the total cost of borrowing in dollars, not just the rate?
2. Is the rate fixed or variable, and what does it track if it moves?
3. How often is interest compounded and added to the balance?
4. What is the penalty if I pay the loan off early?
5. What happens if I miss a payment — fees, rate change, collection activity?
6. Is this lender licensed in my province, and who do I complain to if something goes wrong?

On that last question: complaints about federally regulated financial institutions go to the Financial Consumer Agency of Canada — see FCAC — complaints — while most other lenders are licensed and supervised provincially, and each province and territory has a consumer protection office, listed at FCAC — provincial and territorial regulators.

When borrowing makes things worse

If the only loan available to you costs more than you can realistically repay, taking it will not improve your situation. A consumer proposal stays on your credit report for three years after completion, or six years from filing, whichever comes first. A first bankruptcy stays on your credit report for six years after discharge. Only a licensed insolvency trustee can administer either one, and trustees are regulated by the Office of the Superintendent of Bankruptcy Canada.

Decisions about debt you cannot manage deserve a licensed professional — a trustee, a credit counsellor, or a lawyer — not a search engine at midnight. For background on how borrowing works before you reach that point, FCAC — debt and borrowing is a useful, non-salesy read.

LoanGoose is a loan matching and comparison service, not a lender. The lowest rates are only available to the most qualified applicants.