Extra Mortgage Payment Calculator
On a $300,000 mortgage at 6.5% with 30 years left, an extra $200 a month pays the loan off 6 years, 11 months early and saves $103,449 in interest.
Your mortgage
Everything stays in your browser. The example is a $300,000 balance at 6.5% over 30 years; replace it with your own numbers.
Your result
Your extra payments save $103,449 in interest and pay the loan off 6 years, 11 months early, in 23 years, 1 month instead of 30 years.
- Regular monthly payment
- $1,896.20
- Principal and interest only
- Total interest, no extras
- $382,633
- Total interest, with extras
- $279,185
Amortization schedule with your extra payments
| Year | Interest | Principal (incl. extras) | Balance at year end |
|---|---|---|---|
| 1 | $19,328 | $5,826 | $294,174 |
| 2 | $18,938 | $6,216 | $287,958 |
| 3 | $18,522 | $6,632 | $281,325 |
| 4 | $18,078 | $7,077 | $274,249 |
| 5 | $17,604 | $7,551 | $266,698 |
| 6 | $17,098 | $8,056 | $258,642 |
| 7 | $16,559 | $8,596 | $250,046 |
| 8 | $15,983 | $9,171 | $240,875 |
| 9 | $15,369 | $9,786 | $231,089 |
| 10 | $14,713 | $10,441 | $220,648 |
| 11 | $14,014 | $11,140 | $209,507 |
| 12 | $13,268 | $11,886 | $197,621 |
| 13 | $12,472 | $12,682 | $184,938 |
| 14 | $11,623 | $13,532 | $171,407 |
| 15 | $10,716 | $14,438 | $156,968 |
| 16 | $9,749 | $15,405 | $141,563 |
| 17 | $8,718 | $16,437 | $125,127 |
| 18 | $7,617 | $17,538 | $107,589 |
| 19 | $6,442 | $18,712 | $88,877 |
| 20 | $5,189 | $19,965 | $68,912 |
| 21 | $3,852 | $21,302 | $47,609 |
| 22 | $2,425 | $22,729 | $24,880 |
| 23 | $903 | $24,251 | $629 |
| 24 | $3 | $629 | $0 |
How it is calculated
The monthly rate is your annual rate divided by 12. Each month, interest is the balance times that rate. Your regular payment (principal and interest) is fixed by the standard loan formula: balance times rate, divided by one minus (1 + rate) to the power of minus the number of months. The part of the payment above the interest reduces the balance, and any extra payment is subtracted from the balance right after. The final payment is cut down to what is left. Interest saved is the total interest with no extras minus the total with them. It assumes a fixed interest rate for the remaining term. Taxes, insurance and escrow are not included, and real servicers round payments to the cent.
The CFPB describes this standard amortization formula; the closed form and the extra-payment handling are written out here and computed by this page. The prepayment penalty limits below are from Regulation Z. They matter only if your note has a penalty, which this calculator does not assume.
- What is amortization and how could it affect my loan? (CFPB): “Lenders use a standard formula to calculate the monthly payment that allows for just the right amount to go to interest and principal”. Read 2026-10-27.
- 12 CFR 1026.43(g)(1), Regulation Z (CFPB), when a penalty is allowed: “A covered transaction must not include a prepayment penalty unless”. Read 2026-10-27.
- 12 CFR 1026.43(g)(2), Regulation Z (CFPB), window for prepayment penalties: “Must not apply after the three-year period following consummation”. Read 2026-10-27.
- 12 CFR 1026.43(g)(2)(ii)(A), Regulation Z (CFPB), cap in years 1 and 2: “2 percent, if incurred during the first two years following consummation”. Read 2026-10-27.
- 12 CFR 1026.43(g)(2)(ii)(B), Regulation Z (CFPB), cap in year 3: “1 percent, if incurred during the third year following consummation”. Read 2026-10-27.
Current average mortgage rates: Freddie Mac PMMS.
Extra mortgage payments: common questions
How much does an extra $100 a month save on a mortgage?
On a $300,000 loan at 6.5% with 30 years left, an extra $100 a month saves $60,995 in interest and cuts 4 years off the loan. Your own balance, rate and term change the result, so enter them above.
Is one big extra payment better than small monthly ones?
Money paid earlier saves more interest, because it stops accruing sooner. In the same example, $10,000 paid once at month 1 saves $53,602 (2 years, 9 months early). An extra $2,400 once a year, which is $200 a month spread over the year, saves $99,670 (6 years, 9 months early).
Does an extra payment lower my monthly payment?
No. On a fixed-rate loan the required payment stays the same. Extra principal shortens the loan instead, so the last payment arrives sooner. Lowering the payment usually needs a recast or a refinance, which your servicer can explain.
Can my lender charge a penalty for paying extra?
Only if your note allows one. For most mortgages taken out since January 10, 2014, Regulation Z allows a prepayment penalty only on certain fixed-rate qualified mortgages, never after three years, and caps it at 2% of the balance prepaid in the first two years and 1% in the third. Whether it hits partial prepayments or only a full payoff depends on your note, so check it or ask your servicer.
What mortgage rate should I enter?
On a fixed-rate loan, use the rate on your note. This calculator assumes the rate stays the same for the whole remaining term, so it does not model adjustable-rate resets. If you are comparing offers, Freddie Mac publishes weekly average rates at freddiemac.com/pmms. This page does not repeat those figures, because the rate you get depends on your own loan.
Money that goes into your mortgage is money that does not grow elsewhere. To compare, try the compound interest calculator or the S&P 500 DCA calculator.
This is an educational tool, not financial or mortgage advice. It does not know your loan terms, fees or tax situation.