Amortization Calculator
Adjust the inputs below. Results update as you type.
How it works
An amortization schedule turns a loan into a month-by-month story: how much of each payment is interest, how much is principal, and how the balance declines. That view matters because two loans with similar payments can have very different interest totals and equity build rates.
Provide principal, annual rate, and term. The calculator builds the payment, then walks each period: interest = balance × periodic rate; principal = payment − interest; new balance = old balance − principal. Early rows are interest-dominated; later rows flip toward principal. Annual summaries help when you want tax-year interest totals or a year-by-year equity picture without reading hundreds of monthly lines.
Use the schedule to stress-test extra payments. Applying an extra amount to principal shortens the remaining term and reduces future interest because every later period charges interest on a smaller balance. Confirm whether your lender applies extras to principal immediately and whether biweekly or “skip a payment” products change the calendar. This tool does not model negative amortization, interest-only windows, or ARM resets.
Input guidance
- Principal should match the financed balance after down payment.
- Use the note rate/APR consistent with how your lender states periodic interest.
- Term in months must match the amortization length on the note.
The formula
Each period: interest = balance × monthly rate; principal = payment − interest; new balance = balance − principal. Repeat until the balance reaches zero to build the full amortization schedule.
Worked example
On a $200,000 loan at 6% for 30 years (payment ≈ $1,199), the first month's interest is $1,000 and only $199 goes to principal. By year 20 the split has reversed toward principal.
More examples to test
- $250,000 at 6.25% for 360 months: inspect year-1 interest vs year-10 interest.
- Same loan with an extra $200/month principal: compare payoff date and interest saved.
How to interpret results
Read early rows for interest share and later rows for equity build. Use annual rollups for tax-year interest estimates, then confirm with lender statements.
When this can be inaccurate
Interest-only periods, negative amortization, and ARM resets will not match a level fixed schedule.
Change history
- July 2026: Documented annual summary use and extra-payment interpretation.
- June 2026: Schedule builder and interest totals reviewed.
Site-wide corrections also appear on the corrections log.
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Frequently asked questions
What is an amortization schedule?+
A month-by-month table showing how each payment divides between interest and principal, and how the balance declines until it is fully repaid.
Why does principal grow over time?+
As the balance shrinks, the interest portion of each fixed payment falls, leaving more of the payment to reduce principal.
How do extra payments change the schedule?+
Extra principal payments move you down the schedule faster, removing future interest and shortening the payoff date.
How should I use this result?+
Treat it as a planning estimate. Compare at least two realistic scenarios, then confirm with statements, quotes, or a qualified professional before acting.
How often should I refresh assumptions?+
Refresh whenever rates, income, costs, or policy limits change materially, and before making irreversible commitments.
Guided next steps
Want the full workflow? Use this calculator inside a step-by-step guide.