Amortization Calculator

Formula

PMT = P×r/(1−(1+r)^−n). Balance_k = P(1+r)^k − PMT×((1+r)^k−1)/r. Interest_k = Balance×r.

Extra $E shortens term: solve smallest N with Balance_N ≤ 0 at payment PMT+E.

How it works

Enter loan amount, term, rate, and start date. The engine solves the level-payment formula, then walks every period: interest equals balance times periodic rate, principal equals payment minus interest, balance falls by principal plus any extra. Year rows accumulate the same walk, so the printed schedule, yearly totals, and payoff date always agree. Adding an extra monthly, yearly, or one-time amount re-runs the identical walk with a larger principal slice.

Assumptions

• Fixed rate and fixed schedule; no rate resets or skipped payments.
• Extra payments go entirely to principal in the period paid.
• Zero-interest loans divide principal evenly; rounding favors final payment.

Default result

With Defaults: $200,000 loan, 15 years, 6% APR, monthly payments, no extras, start January 2026 (payment and totals do not depend on start month; only the payoff calendar date does): payment $1,687.71/mo × 180 = $303,788.46 total · interest $103,788.46

Worked examples

Fifteen-year schedule

$200,000 loan, 15 years, 6% APR, monthly, no extras

payment $1,687.71/mo × 180 = $303,788.46 total · interest $103,788.46 — Example calculated with this calculator's formula.

Thirty-year with extra

$200,000 loan, 30 years, 6% APR, monthly, $200 extra monthly

payment $1,199.10/mo × 252 = $351,875.87 total · interest $151,875.87 — Example calculated with this calculator's formula.

Frequently asked questions

What is an amortization schedule?

An amortization schedule is a table showing each loan payment broken down into interest and principal portions, along with the remaining balance after each payment. It provides a complete roadmap of how your loan is paid off over time.

How does an amortization schedule work?

Each payment is divided between interest and principal. Early in the schedule, most of the payment goes toward interest. As the balance decreases, more of each payment goes toward principal. This is called the amortization curve.

How do extra payments affect my amortization schedule?

Extra payments directly reduce the principal balance, accelerating the payoff. This saves interest and shortens the loan term. Even small extra payments can make a significant difference over the life of the loan.

What is the difference between amortization and depreciation?

Amortization in lending is the process of paying off a loan over time. Depreciation is the accounting method of spreading the cost of a tangible asset over its useful life. Both involve spreading costs over time.