How do you calculate a mortgage payment? It comes down to a simple question: how much will I pay each month, and how much of that goes to interest? A mortgage payment calculator gives you the figure in 30 seconds without telling you where it comes from. This guide does, Quebec 2026 edition: the payment formula, the Canadian semi-annual compounding that calculators apply without saying so, the split between principal and interest, how to read an amortization schedule and the effect of accelerated payments. In Canada, a payment equals principal + interest, computed with the annuity formula; for a fixed rate, though, interest is compounded twice a year, not every month as in the United States. And if you're buying an income property, that payment becomes the first input in your cash flow.
Key takeaways
- A payment equals principal + interest. In Canada, the fixed rate is compounded semi-annually (variable is usually monthly).
- The formula:
M = P × c(1+c)^n / [(1+c)^n − 1](P = principal, n = number of payments, c = periodic rate).- Longer amortization means a lower payment but far more interest: going from 25 to 30 years on $500,000 at 5% adds ~$88,000 in interest.
- Accelerated bi-weekly works out to an implicit 13th monthly payment a year, which cuts years off your amortization; non-accelerated bi-weekly saves almost nothing.
- The payment is not your borrowing capacity or your return: check it in a tool.
The mortgage payment formula (explained simply)
We use the annuity formula. In Canada, the periodic rate accounts for semi-annual compounding on a fixed rate; that's the detail calculators apply without showing it.
Payment formula
M = P × c(1+c)^n / [(1+c)^n − 1]M = the payment · P = the principal borrowed · n = the total number of payments · c = the periodic rate.
The Canadian twist is in the c. For a fixed rate, c = (1 + rate/2)^(2/p) − 1, where p is the number of payments per year. The rate/2 reflects the semi-annual compounding required by law (Canadian convention; FCAC). For a variable rate, the calculation is monthly instead.
Why does it matter? At an equal posted rate, semi-annual costs a little less than monthly: 5% nominal gives an effective annual rate (EAR) of 5.06% semi-annually, versus 5.12% monthly (Canadian convention). The EAR is the true rate once compounding is included; it's what lets you compare two offers.
Action point: to compare two loans, look at the EAR, not just the posted rate. For the detail of the interest cost, see our guide on calculating mortgage interest.
Principal or interest: how your payment splits
At the start, the biggest share of the payment goes to interest; over time, the share that repays principal climbs. A worked example shows it better than a long explanation.
Take a loan of $500,000, fixed rate 5%, amortization 25 years, monthly payments.
- Periodic rate:
c = (1 + 0.05/2)^(2/12) − 1 = 0.41239%. - Number of payments:
n = 25 × 12 = 300(the amortization converted into months). - Monthly payment: the formula, with P, c and n, gives $2,908.02 (WiseRock recalculation; nesto model).
- First payment: interest = balance × periodic rate = 500,000 × 0.41239% = $2,061.96; principal = 2,908.02 − 2,061.96 = $846.07.
In other words, on that first payment, 71% goes to interest and only $846.07 reduces your debt. That's exactly why repaying faster (see below) changes the total cost so much.
Action point: look at the "principal" share of your first payment, because that's the real pace at which you build your equity. Check yours with the mortgage calculator.
Mortgage amortization: 20, 25 or 30 years?
Amortization is the total planned time to repay everything. The longer it is, the lower the payment, but the more interest you pay in total. Here's the same $500,000 loan at 5% over three amortization lengths.
| Amortization | Monthly payment | Total interest paid |
|---|---|---|
| 20 years | $3,285.63 | $288,550 |
| 25 years | $2,908.02 | $372,407 |
| 30 years | $2,668.45 | $460,643 |
(WiseRock recalculation; nesto model.)
That's the trap: going from 25 to 30 years lowers the payment by about $240/month but adds ~$88,000 in interest over the life of the loan (460,643 − 372,407). The gentler monthly payment has a price.
On the rules side, the standard amortization is 25 years in Canada. Since December 15, 2024, 30 years is allowed on an insured loan for first-time buyers and for a newly built home; with 20% down or more (uninsured loan), A-lenders also go up to 30 years (CMHC amortization rules; Canada Gazette).
Action point: test 25 vs 30 years and compare the total interest, not just the monthly payment. The right amount also depends on your down payment.
How to read a mortgage amortization schedule
A mortgage amortization schedule details each payment. Each row shows the starting balance, the interest portion, the principal portion and the ending balance; the principal share grows with each payment. Here are the first three months of our $500,000 loan at 5% over 25 years.
| Month | Starting balance | Interest | Principal | Ending balance |
|---|---|---|---|---|
| 1 | $500,000.00 | $2,061.96 | $846.07 | $499,153.93 |
| 2 | $499,153.93 | $2,058.47 | $849.56 | $498,304.38 |
| 3 | $498,304.38 | $2,054.97 | $853.06 | $497,451.32 |
(WiseRock recalculation; nesto model.)
How to read it: the interest drops a little each month, because it's computed on a balance that shrinks; the principal rises by the same amount. Over the full year 1, you pay $24,510 in interest, repay $10,386 of principal, and the balance falls to $489,614. Most tools let you export this schedule to Excel to keep it.
Action point: spot the month when your "principal" share overtakes the "interest" share; that's the turning point of your amortization. To break down the interest portion, see our dedicated guide.
Accelerated or monthly: the effect on total cost
Paying bi-weekly only saves money if it's "accelerated". The nuance is worth thousands of dollars.
- Accelerated bi-weekly: you take your monthly payment, halve it and pay it 26 times. Here: 2,908.02 ÷ 2 = $1,454.01, paid 26 times = $37,804/year, versus $34,896/year monthly (2,908.02 × 12). That gap works out to an implicit 13th monthly payment each year, which cuts years off the amortization and thousands of dollars of interest (pay off your mortgage faster, FCAC).
- Non-accelerated bi-weekly: your annual payment is simply spread over 26 payments. The saving is limited to a few dollars. The myth comes from confusing the two formulas.
Action point: if your budget allows it, choose accelerated: same lifestyle, years off the loan.
Calculate your payment in 30 seconds (the 5 numbers to enter)
For an exact calculation, a mortgage payment calculator asks for five numbers. Here's where to find them.
- Purchase price of the property.
- Down payment: at least 5% up to $500,000, 10% on the portion from $500,000 to $1.5M, 20% above $1.5M. Under 20%, the CMHC insurance premium (about 2.8% to 4%) is added to the loan (CMHC; FCAC down payment).
- Rate, along with the length of its term: the period, often 5 years, during which your rate is guaranteed. Not to be confused with the amortization, which is the total repayment length.
- Amortization: 25 or 30 years.
- Payment frequency: monthly or accelerated.
The classic trap: entering the wrong principal. Principal = price − down payment + CMHC premium (if the down payment is under 20%). Otherwise, the payment shown is understated.
And for an investor: once you have the payment, feed it into the plex's cash flow before making an offer. The payment is just an input, not the decision.
Action point: enter your five numbers into the mortgage calculator, test 25 vs 30 years, then check whether the deal holds up in the rental investment simulator. The payment is not your borrowing capacity: that depends on your debt ratio too.
Common mistakes
- Using a monthly-compounding formula for a fixed rate. In Canada, the fixed rate is semi-annual; an American formula slightly overstates the payment (Canadian convention).
- Believing "bi-weekly" always saves a lot. False for non-accelerated; only accelerated (the implicit 13th payment) makes a real difference (FCAC).
- Confusing payment and borrowing capacity. The payment calculator doesn't tell you the approved amount: you have to pass the stress test at the higher of 5.25% or your rate + 2%, plus the GDS and TDS ratios (CMHC).
- Forgetting the effect of amortization on total cost. A 30-year amortization lowers the payment but adds ~$88,000 of interest in the example (WiseRock recalculation).
- Ignoring the CMHC premium in the principal. Under 20% down, it is added to the financed amount (CMHC).
- For an investor: stopping at the payment instead of going all the way to cash flow and return (WiseRock).
Action point: before you conclude, ask yourself four questions: right formula (semi-annual)? Accelerated or monthly? CMHC premium included? Cash flow checked?
In short, a mortgage payment equals principal + interest, computed with semi-annual compounding in Canada; the amortization decides the total cost and accelerated payments save years. The logical next step: calculate your mortgage payment, and for an income property, move on to the rental investment simulator.
Transparency and updates. The example amounts are illustrative for June 2026 and recalculated locally; they vary by lender and by your file. Semi-annual compounding applies to fixed rates (variable is monthly instead). Rates move: as an indication in June 2026, the 5-year fixed is around 4% and the Bank of Canada policy rate is 2.25% (held on June 10, 2026). This article explains the calculation; it replaces neither a broker nor the lender's approval.
Sources: Canadian semi-annual compounding convention for the fixed rate and effective annual rate (FCAC; nesto model); CMHC (30-year amortization for first-time buyers and newly built homes since December 15, 2024, down payment tranches, insurance premium); FCAC / Canada.ca (accelerated payments); Bank of Canada (policy rate 2.25%, June 10, 2026); WiseRock recalculation (payment $2,908.02, principal/interest split, 20/25/30-year comparison, schedule excerpt, accelerated $37,804 vs $34,896/year). Figures and rules: June 2026.
About WiseRock
WiseRock is a Quebec platform for homebuyers and real estate investors. We offer free tools, market benchmarks and clear frameworks to evaluate an acquisition with confidence — from your first plex to a multi-unit portfolio.
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