Free Mortgage Amortization Calculator — Payoff Schedule & Overpayments

Loan

Principal

Interest rate

% per year

Term

Repayment frequency Start date Currency

Overpayments (optional)

Extra each period

One-off lump sum

Applied at period #

Summary

Periodic payment: —
Total paid: —
Total interest: —
Payoff date: —
Interest saved: —
Time saved: —

Schedule

#	Date	Payment	Principal	Interest	Extra	Balance
Enter your loan and press Calculate.

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Mortgage amortization calculator (with overpayments)

Take control of your finances with our comprehensive mortgage amortization calculator. Whether you're buying a new home or refinancing, this free online tool helps you visualize your full loan payoff schedule. Model the impact of monthly, yearly, or one-time overpayments to see exactly how much interest you can save and how much sooner you can be debt-free. With real-time updates and zero data tracking, you can plan your path to homeownership with confidence.

How to use it

Enter the loan principal, interest rate, and term (years or months).

(Optional) Add a recurring extra payment or a one-off lump sum and the period it lands on.

Press Calculate, then download the full schedule as CSV for spreadsheets.

When to use it

Comparing a 25-year vs 30-year mortgage on the same principal.

Working out how much faster you'd be debt-free if you added $200 a month.

Deciding whether a year-end bonus is best used as a one-off lump sum overpayment.

Modeling fortnightly vs monthly repayments to see the interest difference.

Building a CSV-backed budget for the next 12 months of principal/interest splits.

Why use this one

Real overpayment modeling — recurring extras and lump sums in one schedule.

CSV export so you can paste the schedule into Excel or Google Sheets.

Privacy: all numbers stay in your browser — no email, no signup, no lead-gen form.

FAQ

Does this calculator handle overpayments?

Yes. You can model both a recurring extra amount each period and a one-off lump sum applied at a specific period. The summary shows your new payoff date, interest saved, and time saved compared to the base schedule.

Which repayment frequencies are supported?

Monthly, fortnightly, and weekly. The interest rate is annualised — the calculator divides it across the per-period count internally, so the math stays correct whichever frequency you pick.

Can I export the full schedule?

Yes. Use Copy CSV to put the whole table on your clipboard, or Download CSV to save a file. The CSV has one row per period with date, payment, principal, interest, extra, and remaining balance — Excel, Numbers, and Google Sheets all open it cleanly.

Are my loan numbers sent anywhere?

No. Principal, rate, term, and overpayment inputs stay in your browser. The math runs locally; only anonymous page-view analytics fire on the page (Cloudflare Web Analytics), and no input field is included in any beacon.

Is the math the same as my bank uses?

It uses the standard amortization formula — fixed periodic payment, interest charged on the remaining balance each period, with extras and lump sums reducing principal before the next interest charge. Banks may round differently or apply daily compounding; expect numbers to be within a cent or two, not bit-identical.

Why does the currency picker only change the symbol?

Because the calculator is currency-agnostic — there is no FX conversion, just a display preference. Whatever currency your principal and rate are in, that is the currency of the schedule.