Interest rates affect real estate markets at a macro level — lower rates encourage buying, higher rates cool activity. But the more important question for an individual buyer is: how does a specific interest rate directly affect how much home I can afford? The answer is more significant than most buyers initially appreciate.
The mechanics: how your rate affects your payment
In Canada, mortgage interest is compounded semi-annually (not monthly, as in the United States). The payment amount for a given mortgage depends on the principal, the amortization period, the interest rate, and the payment frequency. When the rate increases, the payment on the same mortgage increases — and therefore the mortgage amount you can qualify for decreases.
Here is a concrete illustration using a 25-year amortization and monthly payments:
- A $600,000 mortgage at 4% has a monthly payment of approximately $3,157
- A $600,000 mortgage at 5% has a monthly payment of approximately $3,490
- A $600,000 mortgage at 6% has a monthly payment of approximately $3,838
The difference between a 4% and 6% rate on a $600,000 mortgage is approximately $681 per month — over $8,100 per year.
The reverse: how rates affect how much you can borrow
The more relevant question for buyers is: if my maximum comfortable monthly payment is fixed, how much can I borrow at different rates? The answer:
- If your maximum monthly payment is $3,157 (25-year amort):
- At 4%: you can borrow approximately $600,000
- At 5%: you can borrow approximately $543,000
- At 6%: you can borrow approximately $493,000
A 2% rate increase reduces your buying power by roughly $107,000 on a $600,000 budget — without any change in your income or the home itself.
Use our free mortgage calculator to run these numbers for your specific situation.
The stress test adds another layer
Canadian lenders must qualify you not at the rate you will actually pay, but at the higher of your contract rate plus 2%, or 5.25%. This is called the mortgage stress test, and it is designed to ensure you can manage your mortgage if rates rise after you close.
Practically, this means your actual borrowing limit is determined by the stress test rate, not your contract rate. If your contract rate is 4.5%, you must qualify at 6.5%. Your mortgage broker will confirm exactly what you qualify for after applying the stress test.
What this means practically
Understanding the relationship between rates and buying power helps you make better decisions at every stage of the buying process:
- When getting pre-approved, a rate hold locks in today's rate for 90–120 days, protecting your buying power if rates rise during your search.
- When evaluating your budget, understand that your approved amount is a ceiling, not a target. Leave room for rate renewals at higher rates in future years.
- When comparing properties at different price points, the difference in monthly payment — not just list price — is often the more useful number to focus on.
If you'd like help thinking through how current rates affect your specific purchase budget, reach out to us. We work through these numbers with buyers regularly.
