How much interest do you pay on a 30-year mortgage?
At 7.28% (Freddie Mac, October 1, 2026), interest over 30 years is about 146% of the loan. On $400,000 that is about $585,000 in interest alone, on top of the $400,000 you borrowed. At the 2021 low of 2.65%, the same loan cost about 45%. An extra $100 a month at 7.28% saves about $78,000 and ends the loan about 40 months early.
Interest share by rate, 30-year fixed
| Rate | Interest as % of loan | Interest on $400,000 |
|---|---|---|
| 2.65% (2021 low) | 45% | $180,268 |
| 4% | 72% | $287,478 |
| 5% | 93% | $373,023 |
| 6% | 116% | $463,353 |
| 7.28% (Oct 1, 2026) | 146% | $585,266 |
| 8% | 164% | $656,621 |
The percent of loan does not depend on the loan size: at a given rate and term, every borrower pays the same share. The dollar column is the $400,000 example.
Rates: 2.65% is the Freddie Mac Primary Mortgage Market Survey record low (January 2021); 7.28% is the 30-year fixed average for the week of October 1, 2026. Interest figures: standard fixed-rate amortization math, 30-year term, no points, taxes or insurance.
Worked example
- Loan: $400,000 at 7.28% for 30 years, the Freddie Mac average for the week of October 1, 2026.
- Payment = $400,000 x 0.006067 / (1 - 1.006067^-360) = about $2,737.
- Total paid = $2,737 x 360 = about $985,300. Interest = $985,300 - $400,000 = about $585,300, which is 146% of the loan.
- With an extra $100 a month: payment $2,837 pays the loan off in about 320 months. Interest = about $507,000, about $78,300 less, and the loan ends about 40 months early.
- This is principal and interest only. Taxes, insurance and any HOA are extra, and lenders quote their own rates.
What does a mortgage payment look like at today's rates?
Should you pay off a 3% mortgage early? The math most people skip
Sources
- Freddie Mac Primary Mortgage Market Survey: 30-year fixed-rate average, 7.28% for the week of October 1, 2026; record low 2.65% in January 2021.
Retrieved October 19, 2026. The survey covers conforming loans to borrowers with strong credit; your quote will differ.
How this is calculated
The payment uses the standard fixed-rate formula: payment = loan x r / (1 - (1 + r)^-n), where r is the rate divided by 12 and n is the term in months. Total interest is payment x months minus the loan. With an extra amount, the same formula solves for the months until the balance reaches zero. The interest share as a percent of the loan depends only on rate and term, not on the loan size.
Common questions
Why does a 7.28% rate cost 146% of the loan?
Because the rate is charged on the remaining balance for 30 years. Early payments are mostly interest, so the balance falls slowly. Over 360 payments of about $2,737, the total reaches about $985,300 on a $400,000 loan.
Does an extra $100 really save that much?
Yes, because every extra dollar goes straight to principal, so interest stops compounding on it for the remaining term. At 7.28% on $400,000, an extra $100 from day one saves about $78,300 and about 40 months. An extra amount started later saves less.
Is the 2.65% comparison fair?
It is the real record low from the Freddie Mac survey (January 2021), shown so the slider has a floor with meaning. Few borrowers actually got 2.65% with no points.
Does this include taxes, insurance or PMI?
No. It is principal and interest only. Property tax, homeowner's insurance and any mortgage insurance raise the real cost of owning the home.
Is this financial advice?
No. It is a calculator for education. It does not say whether you should borrow, refinance or pay extra.