Mortgage Calculator
Calculate the monthly payment of a fixed-rate mortgage, the total paid, total interest, and the year-by-year amortization schedule — with the option to simulate an extra repayment (monthly or a one-time payment) to see how much you'd shorten the term and save in interest.
How is it calculated?
This uses the French amortization system (constant payment), the most common one for fixed-rate mortgages: payment = P × r × (1+r)^n ÷ ((1+r)^n − 1), where P is the principal borrowed, r the monthly interest rate (annual rate ÷ 12 ÷ 100), and n the total number of monthly payments (years × 12). Each month, the interest is the outstanding principal × r, and the rest of the payment goes toward principal — that's the basis of the amortization schedule. If you add an extra repayment (monthly, a one-time payment, or both), that money directly reduces the outstanding principal instead of the payment, so the loan is paid off sooner and you pay less interest overall; the monthly payment doesn't change.
Examples
150,000 at 3% for 25 years, no extra repayment
Monthly payment of 711.32. You'll pay 63,395.09 in total interest, over 300 payments.
200,000 at 2.5% for 30 years, no extra repayment
Monthly payment of 790.24. You'll pay 84,487.05 in total interest.
150,000 at 3% for 25 years, with 100 extra a month
Same payment of 711.32, but you finish paying in 249 months instead of 300 (4 years and 3 months sooner) and save 11,842.65 in interest.
How the payment changes with the term
Early in any term you pay more interest and less principal, because interest is calculated on the outstanding balance, which starts out as high as it will ever be.
| Term | Monthly payment | Total interest |
|---|---|---|
| 15 years | 1,035.87 | 36,457.04 |
| 20 years | 831.90 | 49,655.14 |
| 25 years | 711.32 | 63,395.09 |
| 30 years | 632.41 | 77,666.18 |
Amortization schedule: the first few years
The proportion of principal versus interest in each payment reverses over time: in the first year, just over half of what's paid is interest; in the final year, almost all of it is principal. This table is illustrative for the 150,000 at 3% over 25 years example — enter your own numbers to see your real schedule.
| Year | Principal paid | Interest paid | Outstanding balance |
|---|---|---|---|
| 1 | 4,091.76 | 4,444.04 | 145,908.24 |
| 2 | 4,216.22 | 4,319.59 | 141,692.02 |
| 3 | 4,344.46 | 4,191.35 | 137,347.57 |
| … | … | … | … |
| 25 | 8,398.70 | 137.10 | 0.00 |
How much you save by paying off early
If you'd rather invest that extra money instead of paying down the mortgage, compare both options in the pay off vs. invest simulator; to see how that same amount would grow if invested with periodic contributions, use compound interest.