Amortization Calculator
Amortization Schedule
| Month↕ | Payment↕ | Interest↕ | Principal↕ | Balance↕ |
|---|---|---|---|---|
| 1 | $1,199.10 | $1,000.00 | $199.10 | $199,800.90 |
| 2 | $1,199.10 | $999.00 | $200.10 | $199,600.80 |
| 3 | $1,199.10 | $998.00 | $201.10 | $199,399.71 |
| 4 | $1,199.10 | $997.00 | $202.10 | $199,197.60 |
| 5 | $1,199.10 | $995.99 | $203.11 | $198,994.49 |
| 6 | $1,199.10 | $994.97 | $204.13 | $198,790.36 |
| 7 | $1,199.10 | $993.95 | $205.15 | $198,585.21 |
| 8 | $1,199.10 | $992.93 | $206.17 | $198,379.04 |
| 9 | $1,199.10 | $991.90 | $207.21 | $198,171.83 |
| 10 | $1,199.10 | $990.86 | $208.24 | $197,963.59 |
| 11 | $1,199.10 | $989.82 | $209.28 | $197,754.31 |
| 12 | $1,199.10 | $988.77 | $210.33 | $197,543.98 |
This amortization calculator turns any fixed-rate loan into a complete month-by-month schedule, showing exactly how each level payment is divided between interest and principal until the balance reaches zero. It computes the monthly payment with the standard annuity formula, then walks the loan forward month by month so you can watch the interest share shrink and the principal share grow over time. The result is the constant payment, the total interest paid, and a full table of every payment in the loan.
Formula
M = P · r(1 + r)^n / ((1 + r)^n − 1)
- M
- Fixed monthly payment
- P
- Original loan amount (principal)
- r
- Monthly interest rate = annual rate ÷ 12 ÷ 100
- n
- Total number of monthly payments = years × 12
How it works
- Enter the loan amount, the annual interest rate, and the term in years. The calculator first derives the fixed monthly payment that retires the loan over term × 12 payments.
- For each month it charges interest on the current balance (balance × rate ÷ 12 ÷ 100), subtracts that from the payment to find the principal portion, and reduces the balance accordingly.
- The schedule lists every month with its payment, interest, principal, and remaining balance, while summary figures report the level payment and the cumulative interest over the full term.
Worked example
A $25,000 loan at 5% annual interest amortized over 5 years.
- Monthly rate r = 5 ÷ 12 ÷ 100 = 0.0041667; payments n = 5 × 12 = 60.
- M = 25,000 × 0.0041667 × 1.0041667^60 ÷ (1.0041667^60 − 1) = $471.78.
- Month 1 interest = 25,000 × 0.0041667 = $104.17, principal = 471.78 − 104.17 = $367.61, leaving a balance of $24,632.39.
The level payment is $471.78 per month, the first month splits into $104.17 interest and $367.61 principal, and total interest over the loan is about $3,306.85.
Frequently asked questions
- Why does the principal portion grow every month?
- Because the payment is fixed while the balance falls, each month charges interest on a smaller balance. Less of the constant payment is needed for interest, so more is left to reduce principal, accelerating payoff toward the end.
- What is the difference between this and a mortgage calculator?
- This tool amortizes a generic loan from just principal, rate, and term without property tax, insurance, or down-payment fields. It works for car loans, personal loans, or any fixed-rate debt where you want the full payment-by-payment breakdown.
- Does it support extra payments or a variable rate?
- No. The schedule assumes a single fixed rate and the same scheduled payment every month. Making extra principal payments would shorten the term and reduce total interest, which this calculator does not model.