What a 1% Interest Rate Difference Actually Costs You
The numbers up front
On a $400,000 30-year mortgage, here's what one percentage point costs:
| Rate | Monthly payment | Total interest | Total cost |
|---|---|---|---|
| 6.5% | $2,528.27 | $510,178 | $910,178 |
| 7.5% | $2,796.86 | $606,869 | $1,006,869 |
| Difference | $268.59/month | $96,691 more | $96,691 more |
One percentage point. Nearly $97,000 over the life of the loan.
What that difference looks like monthly
The $269/month gap is easy to underestimate. That's roughly a car payment. A phone bill and a streaming subscription combined. It's a real line item in your monthly budget — every month for 30 years.
And it compounds in the other direction too — that $269/month adds up to nearly $97,000 over the life of the loan. What starts as a monthly inconvenience becomes a six-figure difference by the time you make the final payment.
Rate differences hit harder the bigger the loan. The same 1% gap on a $600,000 mortgage costs roughly $145,000 extra in interest over 30 years.
What 1% buys you in purchasing power
Flip the question around: instead of asking what a higher rate costs you, ask what a lower rate buys you.
If your budget is $2,528/month, here's how much home you can finance at each rate:
| Rate | Monthly payment | Loan you can afford |
|---|---|---|
| 6.5% | $2,528/month | $400,000 |
| 7.5% | $2,528/month | ~$361,100 |
| Difference | — | ~$38,900 less house |
For the exact same monthly outlay, a 1% rate difference is worth nearly $39,000 in buying power. In most markets, that's the difference between the house you want and a meaningful compromise.
The calculator's comparison mode lets you run this side by side with your actual numbers — plug in two rates and see exactly how your buying power shifts.
When rate differences matter most
On larger loans, the gap widens. The examples above use $400k. At $600k, the same 1% rate difference costs ~$145,000 extra over the loan term. The math scales linearly — every $100k in loan amount adds roughly $24,000 to the lifetime cost of a 1% rate difference on a 30-year term.
Refinancing can recover a rate difference. If rates drop 1% after you close, refinancing typically makes financial sense. Closing costs on a refinance usually run $3,000–$6,000. At $269/month in savings, you break even in 12–22 months — after that, you're ahead.
Locking vs floating is a real decision. During volatile rate periods, a 1% move in either direction can happen in weeks. Knowing what it costs in concrete dollars makes that decision easier. Use comparison mode to model what a lock at today's rate means vs waiting.
Key takeaways
- On a $400k / 30-year loan, a 1% rate difference costs $269/month and ~$97,000 over the life of the loan.
- The same monthly budget buys ~$39,000 less house at 7.5% compared to 6.5%.
- Rate differences scale with loan size — a $600k loan sees ~$145,000 extra interest from a 1% gap.
- Refinancing to capture a 1% rate drop typically pays back closing costs within 1–2 years.
- Even a 0.5% difference is significant — half the impact above, still tens of thousands of dollars.
- Use the calculator's comparison mode to model your specific rate scenarios side by side.
See how your rates compare
Use comparison mode to model two scenarios side by side.