Loan Amortization Calculator
Find your exact monthly payment, total interest cost, and full amortization schedule for any fixed-rate loan.
A $300,000 mortgage at 7% for 30 years has a monthly payment of $1,995.91 and costs $418,528 in interest over the life of the loan. This calculator shows the complete amortization schedule — every payment, principal, and interest row.
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Loan Amortization Calculator
Loan amount · Interest rate · Term · Extra payment
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Loan details
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years
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Summary
Monthly payment
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Total of all payments
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Total interest paid
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| # | Payment | Principal | Interest | Balance |
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How it's calculated
The amortization payment formula
Every fixed-rate loan uses the same formula to calculate the constant monthly payment that will pay off the loan exactly on the last payment date.
Monthly payment = P × r / (1 − (1+r)^-n)
Where:
P = principal (loan amount)
r = monthly interest rate = annual rate ÷ 12
n = total payments = years × 12
Each month:
Interest portion = remaining balance × r
Principal portion = payment − interest
New balance = balance − principal portion
- 1Monthly interest rate—
- 2Monthly payment—
- 3Total cost—
- Amortization
- The process of paying off debt with regular payments. Each payment covers interest first; the remainder reduces principal.
- Principal
- The original loan amount — what you actually borrowed, excluding interest.
- APR (Annual Percentage Rate)
- The annual cost of borrowing including interest and fees. Always compare APR, not just the stated interest rate.
- Extra payment
- Any amount paid beyond the required monthly payment. Goes entirely to principal, reducing interest costs and shortening the loan term.
Disclaimer: this calculator assumes a fixed interest rate and constant monthly payments. Adjustable-rate loans, balloon payments, or other structures will differ. Always verify with your lender.
Frequently asked questions
How does amortization work?
In an amortizing loan, each payment covers the month's interest on the remaining balance, and the rest reduces principal. Because the balance decreases each month, the interest portion shrinks while the principal portion grows — even though the total payment stays constant.
Does paying extra save money?
Yes — dramatically. Extra payments go directly to principal, which immediately reduces future interest. On a $300k 30-year loan at 7%, an extra $100/month saves ~$40k in interest and cuts roughly 5 years off the term. Use the extra payment field to see your savings.
What is the difference between APR and interest rate?
The interest rate is the annual cost of the loan principal. APR includes the interest rate plus fees (origination, points, mortgage insurance, etc.), spread over the loan term. APR is the more complete measure for comparison shopping.
Can I use this for any loan type?
Yes — any fixed-rate, fully amortizing loan: mortgage, auto loan, personal loan, student loan. For adjustable-rate mortgages (ARMs), use the initial fixed rate for the fixed period, but understand your payment will change when it adjusts.