Loan Payment Calculator
Estimate fixed monthly loan payments, total interest, payoff timing, and a full amortization schedule with optional extra monthly payments.
Formula
Monthly payment M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is principal, r is monthly rate, n is months. Zero-interest loans use M = P ÷ n.
Assumptions
- Fixed interest rate for the full loan term.
- Equal monthly scheduled payments (standard amortization).
- Extra payments, when entered, apply to principal after scheduled interest.
- Payment dates use UTC calendar arithmetic from the optional start date.
Limitations
- Estimates only — not a loan offer or financial advice.
- Does not model variable rates, taxes, insurance, fees, or prepayment penalties.
- Lender rounding methods may produce slightly different totals.
Worked example
$20,000 loan at 6% for 5 years
A $20,000 loan at 6% annual interest over 60 months produces a monthly payment of about $386.66. Total interest over the term is about $3,199.
Frequently asked questions
Does this include taxes or insurance?
No. This calculator estimates principal and interest only. Property taxes, insurance, origination fees, and other lender costs are not included.
How are extra monthly payments applied?
Extra payments are applied to principal after the scheduled payment and interest for each period. The schedule shows the mathematical effect only — not a recommendation to pay extra.
How are payment dates calculated?
When you enter a start date, payments use the same calendar day each month when possible. If a month has fewer days (for example, January 31 to February), the date moves to the last day of that month.
Last reviewed: 2026-07-22
Category: Finance
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