How Much Interest Will You Pay on Your Mortgage?
Last updated September 2026
Quick answer
On a $400,000 mortgage at 6.25% over 30 years you will pay about $486,632 in interest — more than you borrowed. Total repayment comes to $886,633 for a $400,000 loan, meaning interest equals 121.7% of the amount borrowed. Three things change that number: your rate, your term, and whether you pay extra principal.
The simple version of the calculation
For a fixed-rate loan you do not need a schedule to get the total:
total interest = (monthly payment × number of payments) − loan amount
$2,462.87 × 360 = $886,633 total paid
$886,633 − $400,000 = $486,633 total interestThat is the whole calculation. The monthly payment itself comes from the standard amortization formula, which solves for the fixed amount that clears the balance in exactly 360 payments.
The reason the number is so large is not a high rate or a bad deal — it is time. You are borrowing a large sum for three decades, and interest is charged every month on whatever remains.
How your rate changes it
Same $400,000, same 30 years, different rates:
| Rate | Monthly payment | Total interest | Total paid | vs 6.25% |
|---|---|---|---|---|
| 4.00% | $1,909.66 | $287,478 | $687,478 | −$199,154 |
| 5.00% | $2,147.29 | $373,021 | $773,021 | −$113,611 |
| 6.00% | $2,398.20 | $463,354 | $863,354 | −$23,278 |
| 6.25% | $2,462.87 | $486,632 | $886,632 | — |
| 7.00% | $2,661.21 | $558,036 | $958,036 | +$71,404 |
| 8.00% | $2,935.06 | $656,619 | $1,056,619 | +$169,987 |
What one percentage point costs
Moving from 6% to 7% on this loan raises total interest from $463,354 to $558,036 — $94,682 more for a single point. The monthly difference is only $263, which is why rate shopping feels less urgent than it is. Half a point is worth roughly $47,000.
How your term changes it
Term is the more powerful lever, and the one most people never consider:
| Term | Monthly payment | Total interest | Saved vs 30 years |
|---|---|---|---|
| 15 years | $3,429.69 | $217,345 | $269,288 |
| 20 years | $2,923.71 | $301,692 | $184,941 |
| 30 years | $2,462.87 | $486,632 | — |
A 15-year loan at the same rate costs $269,288 less in interest. The payment is $966.82 higher — a real constraint, and the reason most people choose 30 years — but the trade is stark: an extra $967 a month buys you $269,288 and fifteen years.
Shorter terms usually carry lower rates too, which widens the gap further.
How extra payments change it
The third lever, and the only one available after closing:
| Extra per month | Total interest | Interest saved | Loan paid off in |
|---|---|---|---|
| $0 | $486,632 | — | 30 yrs |
| $100 | $426,889 | $59,744 | 26 yrs 11 mos |
| $200 | $381,683 | $104,950 | 24 yrs 6 mos |
| $500 | $292,703 | $193,929 | 19 yrs 6 mos |
| $1,000 | $213,507 | $273,125 | 14 yrs 10 mos |
Note that $1,000 a month extra gets you to $213,507 — close to the 15-year loan's $217,345 — without ever committing to the higher required payment.
Worked example
$400,000 loan · 6.25% fixed · 30-year term
$104,950
Less interest
5 yrs 6 mos
Off the loan
Time to pay off
Total interest
Estimates only, based on a 30-year fixed loan at a constant rate — not your actual loan terms. Your servicer’s numbers may differ by a few dollars from rounding.
When you pay it: the front-loaded reality
Total interest is one number, but it does not arrive evenly. Interest is charged on your balance, and your balance is largest at the start:
| Period | Interest paid | Principal paid | Balance at end |
|---|---|---|---|
| Year 1 | $24,867 | $4,687 | $395,313 |
| Years 1–5 | $121,121 | $26,651 | $373,349 |
| Years 1–10 | $232,442 | $63,049 | $336,951 |
After a decade and $295,000 of payments, you have retired $63,049 of a $400,000 debt. Just under half of your lifetime interest is paid in the first ten years.
The consequence: where you are in the loan changes what any action is worth. An extra payment in year 1 saves six times what the same payment saves in year 20. A refinance in year 12 restarts the front-loaded phase.
The number you actually pay may differ
These figures are for principal and interest on a fixed-rate loan held to term. Real life intervenes:
- Most people do not hold for 30 years. If you sell or refinance in year 8, you pay eight years of interest, not thirty.
- Refinancing restarts the clock. A new 30-year loan in year 10 means 40 total years of payments, much of it back in the interest-heavy phase — a lower rate does not automatically mean less total interest.
- Adjustable rates move. On an ARM, total interest is unknowable in advance; you can only model scenarios.
- Escrow is not interest. Property taxes, homeowners insurance and PMI are real costs but are not part of this calculation.
- The deduction, if you itemize. At a 24% marginal rate an itemizer's effective cost is nearer 4.75% than 6.25% — but around 90% of US filers take the standard deduction and get no marginal benefit.
Is $486,632 of interest normal?
Yes, at these rates. It is what borrowing $400,000 for 30 years costs, and it is worth separating two questions that often get tangled:
- Is the interest large? Yes — 121.7% of the amount borrowed.
- Was the loan a mistake? Not necessarily. The alternative was usually paying rent for those 30 years, with no equity at the end. The mortgage bought you 30 years of housing plus an asset.
The useful response is not alarm — it is knowing the number, and knowing which of the three levers you can still pull.
Things to consider
- Compare total interest, not monthly payment, when evaluating any refinance or term change. A lower payment frequently means more total interest.
- Rate shopping is worth real money. A quarter point on this loan is roughly $23,000.
- Extra payments are the lever you keep after closing — and the only one that requires no application, no fee, and no commitment.
- Your horizon changes everything. If you will move in five years, lifetime-interest figures are the wrong frame; look at what you will actually pay before you sell.
Run your own numbers
Track your actual mortgage
The figures on this page are an example loan. MortMetrix builds your full amortization schedule from your real balance, rate and term, then shows exactly what any extra payment does to your payoff date, lifetime interest and equity.
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Frequently asked questions
How much interest do you pay on a $400,000 mortgage over 30 years?
About $486,632 at 6.25%, bringing total repayment to $886,633. At 5% it would be $373,021; at 7%, $558,036. The rate matters enormously over three decades.
Do you really pay more in interest than the house costs?
At current rates on a 30-year loan, yes. $486,632 of interest on $400,000 borrowed is 121.7% of the loan. It happens whenever the rate is high enough and the term long enough — above roughly 6% on a 30-year term, interest exceeds principal.
How much does 1% higher interest cost on a mortgage?
On a $400,000 30-year loan, going from 6% to 7% adds $94,682 in total interest — about $263 a month. Half a point is worth roughly $47,000.
How do I calculate the total interest on my mortgage?
Multiply your monthly principal-and-interest payment by the number of payments, then subtract the original loan amount. For a loan already underway, add the interest you have paid to date to the interest remaining on the schedule.
Does a 15-year mortgage really save that much?
On our example, $269,288 — total interest falls from $486,632 to $217,345. The payment rises by $966.82 a month, which is the real constraint. Paying an extra $1,000 a month on a 30-year loan reaches a similar total without the binding commitment.
Related guides
How to Pay Off Your Mortgage Early
Seven ways to clear a mortgage ahead of schedule, each with the years and interest it saves.
Read moreShould You Pay Off Your Mortgage Early?
A numbers-first framework for the decision — order of operations, the tax angle, and the honest trade-offs.
Read moreWhat Is Mortgage Amortization?
The schedule that splits every payment between interest and principal — and why the split shifts.
Read moreHow Extra Payments Reduce Mortgage Interest
Interest is rate times balance. Shrink the balance once and you shrink every future charge.
Read moreFigures on this page are generated from the same amortization engine that powers the MortMetrix dashboard, using the example loan stated in each table. They are estimates based on a fixed-rate loan at a constant rate and are not your actual loan terms. This is educational information, not financial advice.