Calculator
Result (example values pre-filled — change any field)
- Monthly payment
- $313.36
- Total you repay
- $11,281.09
- Total interest
- $1,281.09
First 6 payments
| Month | Payment | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | $313.36 | $66.67 | $246.70 | $9,753.30 |
| 2 | $313.36 | $65.02 | $248.34 | $9,504.96 |
| 3 | $313.36 | $63.37 | $250.00 | $9,254.96 |
| 4 | $313.36 | $61.70 | $251.66 | $9,003.30 |
| 5 | $313.36 | $60.02 | $253.34 | $8,749.96 |
| 6 | $313.36 | $58.33 | $255.03 | $8,494.93 |
Quick answer
For a fixed-rate loan, payment = P × i ÷ (1 − (1 + i)^−n), where P is the amount borrowed, i the monthly rate and n the number of months. Early payments are mostly interest; later ones are mostly principal[1].
#How does the calculator work?
It uses the standard formula for a loan repaid in equal monthly instalments. The monthly rate is the annual rate divided by 12. Each month, interest is charged on the remaining balance and the rest of the payment reduces the balance. The CFPB describes the pattern: most of an early payment goes to interest, and over time, as the balance falls, more of each payment goes to paying down the principal[1]. The pre-filled values are an example only.
Worked example
The pre-filled example
Borrowing 10,000 at 8% a year for 36 months (computed with code):
- Monthly payment
- $313.36
- Total repaid
- $11,281.09
- Total interest
- $1,281.09
- Month 1 split
- $66.67 interest, $246.70 principal
#How should I read the schedule?
Each row is one monthly payment. The payment stays the same, but the interest part falls a little every month because it is charged on a smaller balance, and the principal part grows by the same amount. In the example, interest drops from $66.67 in month 1 to $58.33 in month 6, while the principal repaid rises from $246.70 to $255.03. Changing the term shows the trade-off clearly: a longer term lowers the monthly payment but raises the total interest you pay over the life of the loan.
#Is the rate I enter the APR?
Enter the loan's interest rate. A disclosed APR can also include fees and other charges[2], so using it here slightly overstates the interest. Compare APRs between lenders, then use this calculator to understand the payment. For credit with no interest but fixed instalments, see how buy now, pay later works; for compounding on savings, the APR ⇄ APY converter; and for credit history, how credit scores work.
The bottom line
A fixed-rate loan payment is a precise formula, and the schedule shows where your money goes each month. Use it to compare terms before you sign, not after.
Frequently asked questions
What if the rate is 0%?
Then the payment is simply the amount borrowed divided by the number of months.
Why does the balance fall slowly at first?
Because interest is charged on a larger balance at the start, so less of each payment is left to reduce it[1].
Does this handle variable-rate loans?
No. It assumes the rate stays the same for the whole term.
Sources
- How does paying down a mortgage work? — Consumer Financial Protection Bureau, 2024 Primary
- What is the difference between a mortgage interest rate and an APR? — Consumer Financial Protection Bureau, 2024 Primary
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