Quick guide
How to use this calculator
- Enter every amount in one consistent currency.
- Enter the rate convention and whole-number period requested by each label.
- Review the result together with the calculator-specific assumptions and exclusions.
Calculation method
Calculation method
Each month applies interest, the scheduled payment, a recurring extra amount, and any one-time extra payment without allowing the balance to fall below zero.
The calculation retains full floating-point precision internally and rounds only for display. Amortization advances one payment period at a time so principal, interest, extra payments, and the final payment remain explicit.
Worked example
Practical example
Compare a 30-year schedule with an extra 200 each month and a one-time payment in month 24.
Each month applies interest, the scheduled payment, a recurring extra amount, and any one-time extra payment without allowing the balance to fall below zero.
Supported inputs
Precision and limits
Visible input limits
Numeric tokens accept at most 60 characters. Amounts are capped at 1e12, annual rates at 1000%, and mortgage schedules at 100 years or 1,200 monthly payments.
Estimate, not an offer
Results model only the entered values. A lender may use different day counts, payment timing, fees, rounding, qualification rules, or contractual allocation.
International scope
No currency, country, tax system, insurance rule, mortgage program, or lender policy is assumed. Location-dependent amounts must be entered explicitly.
Calculator-specific assumptions
Mortgage overpayment, extra-payment, payoff, prepayment, and biweekly-equivalent scenarios belong to this consolidated interaction. Confirm how your lender applies extra amounts.