Amortization Calculator
Enter your loan amount, rate and term to see your monthly payment, total interest and a year-by-year amortization schedule. Add an extra monthly payment to see how much interest you save and how much sooner you pay the loan off.
Free · No sign-up · Runs in your browser · Last reviewed November 2026
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About the Amortization Calculator
An amortization calculator shows how a fixed-rate loan is paid off: each monthly payment covers the interest for the month and the rest reduces the balance. This calculator handles mortgages, car loans, personal loans and student loans, and lets you test extra payments toward principal.
How to use it
- Enter the loan amount, the annual interest rate and the term in years.
- Optionally add an extra amount you will pay each month toward principal.
- Read your monthly payment, total interest, payoff time, interest saved and the yearly schedule.
Amortization example: $300,000 at 6.5% for 30 years
The monthly principal and interest payment is $1,896.20 and the total interest over 30 years is $382,633. Early payments are mostly interest; the balance falls slowly at first and faster later. Selected years of the schedule:
| Year | Interest paid | Principal paid | Ending balance |
|---|---|---|---|
| 1 | $19,401 | $3,353 | $296,647 |
| 2 | $19,177 | $3,578 | $293,069 |
| 3 | $18,937 | $3,817 | $289,252 |
| 4 | $18,681 | $4,073 | $285,179 |
| 5 | $18,409 | $4,346 | $280,833 |
| 10 | $16,745 | $6,009 | $254,328 |
| 15 | $14,445 | $8,310 | $217,677 |
| 20 | $11,263 | $11,491 | $166,996 |
| 25 | $6,864 | $15,890 | $96,912 |
| 30 | $781 | $21,973 | $0 |
How extra payments change the loan
Every extra dollar goes straight to principal, so it also stops future interest on that dollar. On the same $300,000 loan at 6.5%:
| Extra per month | Total monthly payment | Payoff time | Total interest | Interest saved |
|---|---|---|---|---|
| None | $1,896.20 | 30 yrs 0 mo | $382,633 | — |
| $100 | $1,996.20 | 26 yrs 0 mo | $321,639 | $60,995 |
| $200 | $2,096.20 | 23 yrs 1 mo | $279,185 | $103,449 |
| $500 | $2,396.20 | 17 yrs 6 mo | $202,874 | $179,759 |
| $1,000 | $2,896.20 | 12 yrs 9 mo | $141,471 | $241,162 |
Check with your lender that extra payments are applied to principal and that there is no prepayment penalty.
Monthly payment and total interest by rate and term
| Rate | Term | Monthly payment | Total interest |
|---|---|---|---|
| 5.5% | 15 years | $2,451 | $141,225 |
| 5.5% | 20 years | $2,064 | $195,279 |
| 5.5% | 30 years | $1,703 | $313,212 |
| 6.5% | 15 years | $2,613 | $170,398 |
| 6.5% | 20 years | $2,237 | $236,813 |
| 6.5% | 30 years | $1,896 | $382,633 |
| 7.5% | 15 years | $2,781 | $200,587 |
| 7.5% | 20 years | $2,417 | $280,027 |
| 7.5% | 30 years | $2,098 | $455,152 |
The amortization formula
The fixed monthly payment is M = P × i ÷ (1 − (1 + i)−n), where P is the loan amount, i is the monthly rate (annual rate ÷ 12) and n is the number of payments. Each month the interest is the balance times i; the rest of the payment reduces the balance.
Frequently asked questions
What is an amortization schedule?
An amortization schedule lists every payment on a loan and splits it into interest and principal, with the remaining balance after each payment. With a fixed-rate loan the payment stays the same while the interest share shrinks and the principal share grows.
How do I calculate amortization?
Compute the monthly payment with M = P × i ÷ (1 − (1 + i)−n). For each month, interest is the balance times the monthly rate, principal is the payment minus interest, and the new balance is the old balance minus principal.
How much does an extra payment save?
On a $300,000, 30-year loan at 6.5%, paying $200 extra each month shortens the loan to about 23 years 1 months and saves roughly $103,449 of interest.
Why is most of my early payment interest?
Interest is charged on the remaining balance, which is largest at the start. On a $300,000 loan at 6.5% the first payment is about $1,625 interest and only $271 principal.
Does this work for auto loans and personal loans?
Yes. Any fixed-rate loan with equal monthly payments follows the same schedule: mortgages, car loans, personal loans and student loans.
Is a 15-year or 30-year loan better?
A 15-year loan has a higher monthly payment but far less total interest; a 30-year loan keeps the payment lower. Comparing both in the table above and in the calculator shows the trade-off for your own numbers.
What does the calculator not include?
It covers principal and interest only. Property tax, homeowners insurance and HOA fees are not included; use the mortgage calculator for the full payment.
Official sources
Last reviewed: November 2026. Estimates only. Your lender's schedule may differ slightly because of rounding, payment dates and fees.