Mortgage Extra Payment Calculator — Interest & Time Saved

See how much time and interest an extra monthly mortgage payment saves you.

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Formula

Same amortization formula as a standard mortgage, but the monthly payment is increased by the extra amount; the loop runs until the balance reaches zero, which is what shortens the term.

Examples

InputResult
$300,000 at 6%, 30 yrs, +$200/mo279 months · $91,173 interest saved · 6.8 yrs shorter
$400,000 at 6.5%, 30 yrs, +$300/mo269 months · $149,581 interest saved · 7.6 yrs shorter
$25,000 at 7%, 5 yrs, +$100/mo49 months · $939 interest saved · 0.9 yrs shorter

Frequently Asked Questions

How does an extra payment save so much interest?

Extra money goes straight to the principal, so every later month charges interest on a smaller balance — the saving compounds over the whole remaining term.

Is paying extra always worth it?

Only if your loan allows penalty-free prepayment and your rate is higher than what you could safely earn elsewhere. Compare with investing the same amount.

What about biweekly payments?

Paying half the monthly amount every two weeks produces roughly one extra monthly payment per year — a similar effect to an extra payment.

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Disclaimer: This calculator is for informational and educational purposes only and does not constitute financial, investment, tax or legal advice. Results are estimates — actual returns, rates and terms vary. Consult a qualified financial professional before making financial decisions.