What a rate change does to your mortgage
Enter a home price, down payment and rate to see your monthly payment — and what it becomes if rates move by half a point, one point or two.
Your loan
$80,000 down
The starting values are examples, not current market rates or prices.
If rates rise 1 point, this home costs $215 more a month — $77,353 over 30 years. If they fall 1 point, it costs $206 less a month.
| Change | Rate | Monthly | Per month | Per year | Over the loan |
|---|---|---|---|---|---|
| −1 pt | 5.5% | $1,816.92 | −$205.69 | −$2,468 | −$74,049 |
| −0.5 pt | 6% | $1,918.56 | −$104.06 | −$1,249 | −$37,460 |
| Your rate | 6.5% | $2,022.62 | — | — | — |
| +0.5 pt | 7% | $2,128.97 | +$106.35 | +$1,276 | +$38,286 |
| +1 pt | 7.5% | $2,237.49 | +$214.87 | +$2,578 | +$77,353 |
| +2 pt | 8.5% | $2,460.52 | +$437.91 | +$5,255 | +$157,646 |
Principal and interest only — property tax, homeowners insurance, HOA fees and mortgage insurance are not included.
Educational estimate, not financial advice. Everything is calculated in your browser — nothing you enter is sent anywhere or saved.
How this calculator works
The monthly payment uses the standard amortization formula for a fixed-rate loan: payment = L × r / (1 − (1 + r)−n), where L is the loan amount, r the annual rate divided by 12 and n the number of monthly payments. At a 0% rate the payment is simply the loan divided by the number of months. Total interest is all payments minus the loan amount.
The comparison keeps the price, down payment and term fixed and changes only the rate. Rates are not allowed below 0%. The starting values — a $400,000 home, 20% down, 6.5% over 30 years — are examples, not current market figures.
Mortgage rates follow longer-term Treasury yields more closely than the Fed’s policy rate. See how the federal funds rate has moved, why interest on the national debt rises with the same yields, and what the debt comes to per person.
Common questions
How much does a 1% rise in mortgage rates cost?
On a $320,000 30-year loan, going from 6.5% to 7.5% raises the monthly principal and interest from $2,022.62 to $2,237.49 — $214.87 more a month, or $77,353 over the full term. These are example rates, not current market rates.
Does a rate change affect my existing fixed-rate mortgage?
No. A fixed-rate mortgage keeps its rate for the life of the loan. Rate moves matter when you buy, refinance, or hold an adjustable-rate mortgage when it resets.
Why does a small rate change add so much over 30 years?
Early payments are mostly interest, and interest is charged on the whole remaining balance every month. A higher rate raises that charge in every one of 360 payments, so a difference of a couple of hundred dollars a month adds up to tens of thousands over the loan.
Is a 15-year mortgage cheaper?
In total interest, yes, by a wide margin; in monthly payment, no. At 6.5% the same $320,000 loan costs $2,787.54 a month over 15 years against $2,022.62 over 30, but total interest falls from $408,142 to $181,758. Rates on 15-year loans are usually a little lower too.
What is not included in this payment?
Property tax, homeowners insurance, HOA fees and private mortgage insurance (usually required with less than 20% down). Together they often add several hundred dollars a month on top of principal and interest.