Amortization Calculator
Full payment-by-payment schedule with extra payments, a lump sum or a balloon.
How to use Amortization Calculator
- Enter the loan amount and interest rate.
- Give either the term (the payment is calculated) or your monthly payment (the term is calculated).
- Optionally add extra monthly payments, a one-off lump sum or a balloon, then open "Every payment", download the CSV or print.
How it works
Amortization is the gradual repayment of a loan by equal payments. Every month: interest = balance × yearly rate ÷ 12, principal = payment − interest, and the new balance is the old balance minus the principal. Amounts are rounded to cents each month, as lenders do, and the last payment absorbs the rounding.
With a balloon, the regular payment is sized so that the chosen amount is still owed after the last payment: M = (P − B ÷ (1 + r)ⁿ) × r ÷ (1 − (1 + r)⁻ⁿ). When you enter a monthly payment instead of a term, the number of payments is n = −ln(1 − r × P ÷ M) ÷ ln(1 + r), rounded up, with a smaller final payment. If the payment does not cover the first month’s interest, the loan can never be repaid and the tool says so.
Extra payments and a one-off lump sum reduce principal directly. The result shows the interest and time they save compared with the same loan without them.
Example
200,000 at 6% for 30 years: the payment is 1,199.10. In month 1, interest is 200,000 × 0.06 ÷ 12 = 1,000.00, so 199.10 reduces the balance to 199,800.90. Over the full term you pay about 231,676 in interest.
Frequently asked questions
What is an amortization schedule?
A table of every payment showing how much is interest, how much is principal and what is still owed. Early payments are mostly interest; later ones mostly principal.
How do extra payments change the schedule?
They go straight to principal, so less interest builds up in every later month and the loan ends sooner. Enter a monthly extra or a one-off amount and the month you will pay it.
What is a balloon payment?
A large amount left to pay at the end of the term. It lowers the regular payment, but you must pay or refinance the balloon when it falls due.
Can I find how long a loan takes at a payment I choose?
Yes. Choose "Monthly payment" and enter it. The tool shows the number of payments and the payoff month.
Can I export the schedule?
Yes. "Download full schedule (CSV)" opens in Excel, Google Sheets or Numbers, and "Print" gives a paper or PDF copy.
Limitations
- Monthly payments with monthly compounding only.
- Fees, insurance and taxes are not included.
- Lenders using daily interest or different rounding will differ by small amounts.
- For information only. It is not financial advice and not an offer of credit.
Last reviewed November 9, 2026. How we build and test tools.