Mortgage Rate Purchasing Power Calculator
Example: Monthly principal & interest budget: 2500 $ · Current mortgage rate: 6.5 %/yr · Stress rate (e.g. 1–2% higher): 7.5 %/yr
| Purchasing power lost at stress rate | $37,983 |
| Max loan at current rate | $395,527 |
| Max loan at stress rate | $357,544 |
| Purchasing power lost (%) | 9.60% |
| Extra monthly payment if you keep the same loan size | $266 |
Worked example
With a $2,500/month P&I budget: at 6.5%, you can borrow up to $396,000. At 7.5%, that same budget only supports $356,000 — a loss of $40,000 in purchasing power (10%). Alternatively, if you insist on buying the $396,000 home at 7.5%, your monthly payment rises to $2,780 — $280/month more than your budget. One percentage point of rate increase is roughly 10% of purchasing power lost at these rate levels.
Frequently asked questions
How quickly can mortgage rates move?
Mortgage rates can move 0.25–0.5% in a single week during volatile market periods. Rates are driven by the 10-year Treasury yield, Federal Reserve policy expectations, and lender capacity. Locking your rate at application protects you from rate increases during the closing process, typically 30–60 days.
Should I buy now if I think rates will fall?
Rate timing is difficult even for professionals. A common approach is to buy when the home fits your life and budget at current rates, then refinance if rates fall significantly later. Waiting for lower rates while prices rise may result in a smaller net gain than buying now.
Does the down payment also affect purchasing power?
Yes. A larger down payment directly reduces the loan needed, partially offsetting a rate increase. If rates rise, increasing your down payment (if possible) or targeting a lower-priced home are the main levers to keep the payment within budget.