Equal-Principal Mortgage Repayment Calculator
Enter the loan amount, annual interest rate, and term to instantly calculate an equal-principal (constant amortization) mortgage: the first and final monthly payment, total repayment, and total interest. The constant-principal method also shows a year-by-year table of principal, interest, and remaining balance.
Input
× 10k
%
yrs
Result
First monthly payment
$96,428.00
Decreases to $71,728.00 by the final payment
Monthly principal
$71,428.00
Total interest
$5,262,541.00
Total repayment
$35,262,541.00
Year-by-year breakdown
| Year | Principal | Interest | Payment | Balance |
|---|---|---|---|---|
| Year 1 | $857,136.00 | $296,070.00 | $1,153,206.00 | $29,142,864.00 |
| Year 2 | $857,136.00 | $287,501.00 | $1,144,637.00 | $28,285,728.00 |
| Year 3 | $857,136.00 | $278,928.00 | $1,136,064.00 | $27,428,592.00 |
| Year 4 | $857,136.00 | $270,357.00 | $1,127,493.00 | $26,571,456.00 |
| Year 5 | $857,136.00 | $261,786.00 | $1,118,922.00 | $25,714,320.00 |
| Year 6 | $857,136.00 | $253,215.00 | $1,110,351.00 | $24,857,184.00 |
| Year 7 | $857,136.00 | $244,644.00 | $1,101,780.00 | $24,000,048.00 |
| Year 8 | $857,136.00 | $236,071.00 | $1,093,207.00 | $23,142,912.00 |
| Year 9 | $857,136.00 | $227,502.00 | $1,084,638.00 | $22,285,776.00 |
| Year 10 | $857,136.00 | $218,928.00 | $1,076,064.00 | $21,428,640.00 |
| Year 11 | $857,136.00 | $210,358.00 | $1,067,494.00 | $20,571,504.00 |
| Year 12 | $857,136.00 | $201,786.00 | $1,058,922.00 | $19,714,368.00 |
| Year 13 | $857,136.00 | $193,216.00 | $1,050,352.00 | $18,857,232.00 |
| Year 14 | $857,136.00 | $184,644.00 | $1,041,780.00 | $18,000,096.00 |
| Year 15 | $857,136.00 | $176,072.00 | $1,033,208.00 | $17,142,960.00 |
| Year 16 | $857,136.00 | $167,502.00 | $1,024,638.00 | $16,285,824.00 |
| Year 17 | $857,136.00 | $158,929.00 | $1,016,065.00 | $15,428,688.00 |
| Year 18 | $857,136.00 | $150,359.00 | $1,007,495.00 | $14,571,552.00 |
| Year 19 | $857,136.00 | $141,786.00 | $998,922.00 | $13,714,416.00 |
| Year 20 | $857,136.00 | $133,216.00 | $990,352.00 | $12,857,280.00 |
| Year 21 | $857,136.00 | $124,644.00 | $981,780.00 | $12,000,144.00 |
| Year 22 | $857,136.00 | $116,073.00 | $973,209.00 | $11,143,008.00 |
| Year 23 | $857,136.00 | $107,502.00 | $964,638.00 | $10,285,872.00 |
| Year 24 | $857,136.00 | $98,930.00 | $956,066.00 | $9,428,736.00 |
| Year 25 | $857,136.00 | $90,360.00 | $947,496.00 | $8,571,600.00 |
| Year 26 | $857,136.00 | $81,786.00 | $938,922.00 | $7,714,464.00 |
| Year 27 | $857,136.00 | $73,217.00 | $930,353.00 | $6,857,328.00 |
| Year 28 | $857,136.00 | $64,644.00 | $921,780.00 | $6,000,192.00 |
| Year 29 | $857,136.00 | $56,073.00 | $913,209.00 | $5,143,056.00 |
| Year 30 | $857,136.00 | $47,502.00 | $904,638.00 | $4,285,920.00 |
| Year 31 | $857,136.00 | $38,931.00 | $896,067.00 | $3,428,784.00 |
| Year 32 | $857,136.00 | $30,360.00 | $887,496.00 | $2,571,648.00 |
| Year 33 | $857,136.00 | $21,787.00 | $878,923.00 | $1,714,512.00 |
| Year 34 | $857,136.00 | $13,218.00 | $870,354.00 | $857,376.00 |
| Year 35 | $857,376.00 | $4,644.00 | $862,020.00 | $0.00 |
How it works
- The equal-principal (constant amortization) method keeps the principal portion of each payment constant and adds interest on the remaining balance on top. As the balance shrinks, the payment gradually falls and the total interest is lower than an equal-payment (annuity) loan, but the burden is heaviest at the start.
- The monthly principal = loan amount ÷ number of payments (rounded down to the nearest unit) and stays constant. Any remainder is settled in the final payment so the balance reaches exactly zero.
- Each payment's interest = remaining balance × monthly rate (annual rate ÷ 12), rounded to the nearest unit, and the payment = principal portion + interest. The first payment is the largest and it decreases over time.
- The table sums the principal, interest, and payment for each year (12 installments) and shows the remaining balance at the end of that year.
- Calculations assume a fixed rate for the entire term. Variable rates, fixed-period options, bonus payments, early repayment, credit life insurance, and fees are not considered.
- Results are rounded approximations with any remainder settled in the final payment. Actual amounts may differ depending on your lender's calculation and rounding rules. Make any borrowing decision at your own discretion.
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Equal-Principal Mortgage Repayment Calculator