Amortization Schedule Calculator
Calculate your monthly mortgage or loan payment and see a year-by-year breakdown of principal vs. interest over the life of your loan.
Loan amortization is the process of paying down a loan through fixed periodic payments, where each payment covers both interest and principal. Early payments are mostly interest; later payments are mostly principal. Understanding amortization helps you see exactly how much a loan really costs.
Monthly payment formula: M = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1]
Where:
- M = monthly payment
- P = principal (loan amount)
- r = monthly interest rate = Annual Rate ÷ 12
- n = total number of payments = Years × 12
Interest portion of any payment: Interest = Remaining Balance × Monthly Rate
Principal portion: Principal Paid = M − Interest
Worked example: $250,000 mortgage, 6.5% annual rate, 30-year term.
r = 6.5% ÷ 12 = 0.5417% = 0.005417 n = 30 × 12 = 360 payments
M = 250,000 × [0.005417 × (1.005417)³⁶⁰] ÷ [(1.005417)³⁶⁰ − 1] M = $1,580.17/month
First payment breakdown: Interest = $250,000 × 0.005417 = $1,354.17 Principal = $1,580.17 − $1,354.17 = $226.00
Total paid over 30 years: $1,580.17 × 360 = $568,861, which means $318,861 of interest on a $250,000 loan. You pay for the house, and then you pay for it again.
Key insight: extra payments Add $200 a month to the mortgage above and the loan clears in 22 years and 1 month instead of 30. That is 7.9 years early, and the interest falls from $318,861 to $221,243, a saving of $97,618.
The reason it works so hard is that an extra payment skips the interest calculation entirely and goes straight at the balance. Every dollar of principal you retire early also retires all the future interest that dollar would have generated. In this case $53,000 of extra payments buys back $97,618 of interest, which is a return no savings account is going to match. Put a figure in the extra payment box and the schedule below reflects it.
Typical loan terms:
- Mortgage: 15 or 30 years
- Auto loan: 3–7 years
- Personal loan: 1–5 years
- Student loan: 10–25 years
Refinance break-even rule
Refinancing makes sense when (monthly savings × months you’ll actually keep the loan) exceeds the closing costs. With typical closing costs of $3,000 to $6,000 on a mortgage, the break-even point usually lands 18 to 36 months out. If you plan to sell or move before then, refinancing doesn’t pay off no matter how attractive the new rate looks. Run the math both ways: the savings on the new rate AND the realistic months you’ll hold the loan.
Rate must match payment frequency
The formula’s “r” is the rate per payment period, not the annual rate. For a monthly-payment loan use r = annual ÷ 12; for a weekly-payment loan use r = annual ÷ 52. Plugging the annual rate directly produces a wildly wrong payment, overstated by orders of magnitude in some cases.
Want the individual payments instead?
This page rolls the loan up year by year, which is the right shape for “what does this cost me and what would an extra $200 do”.
If you want to read a specific stretch payment by payment, say months 85 to 108 because that is where you are now, use the month-by-month amortization table. It prints any window of the loan and tells you which payment is the one where principal finally overtakes interest.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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