How a 1% Rate Change Affects Your Mortgage Payment in Alberta
Short answer
A 1% (100 basis point) rate increase on a new fixed-rate mortgage typically adds roughly $55–$65 per month per $100,000 borrowed over a 25-year amortization — a planning rule of thumb. The exact change depends on balance, amortization, compounding, and whether the change is to your contract rate or only to the stress test qualifying rate.
The plain-English version
Interest rate changes affect payment through the standard mortgage payment formula with Canadian semi-annual compounding for fixed rates. On larger balances the dollar impact is significant: 1% on $500,000 is roughly $275–$325/month. On shorter remaining amortizations the same rate change hits payments harder because principal is paid down over fewer months.
For variable mortgages, a 1% prime increase may not immediately change your payment on a fixed-payment VRM — instead it slows principal paydown or pushes you toward the trigger rate. On an ARM, a 1% increase flows through to a higher payment on the next adjustment date. Always model your specific product type.
Alberta-specific considerations
- Alberta buyers using the stress test face qualification at contract rate plus 2% — a 0.50% market rate rise can reduce buying power by more than the payment alone suggests.
- Property tax and heating in GDS/TDS ratios mean a rate-driven payment increase is not your only affordability variable.
- Renewal borrowers with large balances and 15–20 years remaining amortization feel 1% moves sharply — shop before maturity.
Example scenario
A $450,000 mortgage at 5.29% over 25 years has a payment of about $2,690/month (planning estimate). At 6.29% — 1% higher — the payment rises to about $2,950/month, an increase near $260/month. Use the payment calculator with your exact balance and rate for precision.
Common mistakes to avoid
- Using U.S. mortgage calculators that ignore Canadian semi-annual compounding.
- Applying the 1% rule to remaining amortization at renewal without recalculating — the balance is lower but the term may be shorter.
- Forgetting that a 1% rise on variable may not change payment immediately on a VRM.
- Ignoring that qualification uses a rate 2% above contract — buying power shrinks faster than payment at contract rate.