Find the fixed monthly payment for a loan amount, interest rate, and term.
A fixed monthly payment of 452.94 pays off 15,000 over 36 months at 5.5% annual interest.
This calculator finds the fixed periodic payment required to fully repay a loan over a set term at a given interest rate — the same core math used for mortgages, auto loans, and personal loans, applied generally to any amortizing debt.
P is the principal, r is the periodic interest rate, and n is the total number of payments. Doubling the loan term roughly halves the monthly payment but typically more than doubles the total interest paid, because the balance stays outstanding — and accruing interest — for much longer.
| Term | Payment | Total paid |
|---|---|---|
| 3 years | $617 | $22,224 |
| 5 years | $396 | $23,760 |
| 7 years | $304 | $25,536 |
$20,000 loan at 7% — monthly payment vs. total paid by term
Example 1 — Weekly payment schedule: A $8,000 loan at 9% over 2 years paid weekly (104 payments) works out to about $79/week, using a weekly periodic rate of 9%/52 in the same formula.
Example 2 — Biweekly payment schedule: The same $8,000 loan paid biweekly (52 payments over 2 years) comes to about $158 every two weeks, slightly less total interest than monthly payments due to more frequent principal reduction.
Example 3 — Solving for the affordable loan amount from a target payment: If you can afford $400/month at 6% over 5 years, rearranging the formula shows you can borrow up to roughly $20,700 — useful for figuring out a maximum loan size before shopping.
| Frequency | Payment | Total interest |
|---|---|---|
| Monthly (60 payments) | $396 | $3,760 |
| Biweekly (130 payments) | $183 | $3,790 |
| Weekly (260 payments) | $91 | $3,660 |
Does this work for any type of loan? Yes, the fixed-payment amortization formula applies to any loan with equal periodic payments and a fixed rate.
What if my loan has a variable rate? Variable-rate loans recalculate the payment (or the amortization schedule) whenever the rate changes, so this formula only gives a snapshot at the current rate.
Why does a small rate change affect my payment so much on a long-term loan? Because interest compounds over more periods, so its share of the fixed formula grows disproportionately on longer terms.
How do I calculate the maximum loan amount I can afford from a target payment? Rearrange the payment formula to solve for principal (P), plugging in your affordable payment, the rate, and the term — this reverses the usual calculation direction.
Does switching from monthly to biweekly payments always save money? It usually does slightly, mainly because 26 biweekly half-payments equal 13 monthly payments per year — one extra "payment" annually accelerates payoff modestly compared to strictly monthly payments.
What's the difference between this and an amortization calculator? This tool solves for the single fixed payment amount; an amortization calculator additionally breaks that payment down period-by-period into principal and interest over the full schedule.
Why is the total paid so much higher than the loan amount on a long-term loan? The difference is accumulated interest — the longer the balance remains outstanding, the more total interest accrues, even though the rate and payment structure stay fixed.
For a $50,000 loan at 6% annual interest over 10 years (120 monthly payments), the payment works out to roughly $555/month — increasing the rate to 8% with everything else unchanged raises the payment to about $606/month, an increase of over $6,000 total across the loan term.
Amortizing loan: A loan repaid through equal periodic payments that cover both principal and interest.
Periodic rate: The interest rate applied per payment period, typically the annual rate divided by the number of periods per year.