How to calculate mortgage payments in Canada.

Why semi-annual compounding makes your Canadian payment different

Here’s the rule almost every generic mortgage explainer gets wrong for Canada: fixed-rate mortgages compound semi-annually, not monthly. This comes from Canada’s Interest Act: section 6 requires a blended-payment mortgage to state its rate calculated yearly or half-yearly, not in advance¹, and half-yearly is the Canadian convention for fixed rates.

What does that mean in practice? A rate posted as, say, an annual figure isn’t simply divided by 12 to get your monthly rate the way it would be south of the border. Instead, the rate is treated as compounding twice a year, and you convert that into an equivalent monthly rate before applying the formula. The effect is subtle but real: the same posted rate compounded semi-annually produces a slightly lower effective annual rate — and therefore a marginally smaller payment — than it would compounded monthly. On a large mortgage over decades, “marginal” still adds up to real money.

One important exception: this rule applies to fixed-rate mortgages. Variable-rate mortgages in Canada typically compound monthly. So when you’re comparing a fixed and a variable quote, you’re not quite comparing apples to apples on the compounding math — another reason to run both through a calculator that handles the distinction rather than estimating in your head.

Amortization, term, and the principal-vs-interest split

Two words get confused constantly, and the difference changes your payment. Amortization is the full length of time to pay the mortgage to zero — most commonly 25 years, or up to 30 for uninsured mortgages and, since December 15, 2024, for insured first-time buyers and new-build buyers². It’s the n in the formula and it directly sets the payment size: a longer amortization spreads the debt over more payments, so each one is smaller, but you pay far more total interest over the life of the loan. Term is different — it’s the length of your current contract (often 1 to 5 years), after which you renew at whatever rate is available then. Your payment is calculated on the amortization; your rate is only locked for the term.

Within each payment, the split between principal and interest shifts over time. Every period, the lender charges interest on the outstanding balance first; whatever’s left of your payment reduces the principal. Early on, the balance is large, so the interest charge eats most of the payment and only a sliver goes to principal. As the balance falls, the interest portion shrinks and more of each payment attacks the principal — so your equity builds slowly at first and then accelerates. You can see this play out payment by payment in the schedule our amortization calculator generates, which is the clearest way to understand where your money actually goes.

How payment frequency changes the math

Payment frequency is the lever most borrowers overlook, and it’s the one that can quietly save you the most. Monthly is the baseline — twelve payments a year. Semi-monthly (24 payments) and bi-weekly (26 payments) usually just slice the monthly amount to fit the calendar, so your yearly total is roughly unchanged and so is your amortization.

Accelerated frequencies are where the magic happens. An accelerated bi-weekly payment is calculated as exactly half your monthly payment, paid every two weeks. Because there are 26 two-week periods in a year — not 24 — you end up making the equivalent of 13 monthly payments instead of 12. That extra payment goes straight to principal, shortening a 25-year amortization by several years and saving a meaningful chunk of total interest, all without a painful change to your budget. Accelerated weekly works the same way with 52 payments.

The trade-off is purely cashflow: accelerated schedules take slightly more out of your account each year. Whether that’s worth it depends on your budget — which is exactly the kind of comparison our bi-weekly payment calculator is built to show you side by side, so you can see the interest saved before committing.

From the formula to your real numbers

Understanding the math is the point of this guide — but you shouldn’t have to run exponents by hand every time you want to test a scenario. The practical workflow is to grasp the concepts here, then use the tools to do the arithmetic: our payment calculator for a quick figure, the amortization calculator for the full schedule, and the affordability calculator to work backward from a payment you can comfortably carry to the mortgage it supports.

Where the numbers turn into a real decision, that’s where a broker earns their keep. Knowing your payment is one thing; knowing which lender, rate type, amortization, and frequency actually fit your situation — and qualify you under the stress test — is another. As an independent brokerage with access to 100+ lenders and FSRA licence #13737, Mortgage Squad Advisors runs your exact figures across the market and shows you the real payment options in writing, with every rate and fee disclosed. You can also just ask Maya, our AI assistant, to walk through your numbers any time — or start a no-obligation pre-approval to see what you actually qualify for.