Mortgage Prepayment Calculator

Enter the loan amount, interest rate and term, then your planned prepayment amount and month. This tool compares "no prepay" vs "prepay now" and gives you the interest saved under both shorten the term and lower the monthly payment.

How to use

Enter loan amount, interest rate, term and pick a currency.
Enter prepayment amount and the month you plan to prepay.
Choose whether to shorten the term or lower the monthly payment, then submit.

How the calculation works

Equal-installment monthly payment = P · i · (1+i)^n ÷ ((1+i)^n − 1), where i = annual rate / 1200. Equal-principal monthly payment = P/n + remaining · i. The tool simulates each month, subtracting prepay amount from remaining principal at the prepay month and comparing total interest. Source: Wikipedia — Amortization calculator

FAQ

Should I shorten the term or lower the payment?

Shortening the term usually saves more total interest (you stop paying the bank for less time). Lowering the payment reduces your monthly burden but you still pay for the full original term. Choose based on cash-flow priorities.

Does prepaying have a penalty?

Some lenders charge a penalty if you prepay before a minimum period (often 1 year). Check your loan contract.

Why does my bank's number differ slightly?

Banks usually compute interest daily, apply rate adjustments on repricing dates, and may add fees. This tool uses a standard monthly model for relative comparison.

Why does currency only affect the symbol?

The mathematical algorithm is identical across currencies. Only the display symbol changes. Real-world interest rates vary by country — you enter the rate directly.

References

Wikipedia — Amortization calculator (https://en.wikipedia.org/wiki/Amortization_calculator)
Wikipedia — Mortgage loan (https://en.wikipedia.org/wiki/Mortgage_loan)

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