How to Use

Enter your loan details. Fill in the loan amount, annual interest rate, and loan term in years. Optionally add an extra monthly payment to see how much interest you save.
Review the results. Monthly payment, total interest, total cost, and payoff date appear instantly. The pie chart visualizes principal vs. interest distribution.
Export the schedule. Click Export CSV to download a month-by-month amortization schedule for your spreadsheet, accountant, or records.

Why Use This Tool

All math runs locally in your browser using standard amortization formulas — the same equations banks use. No server roundtrip, no privacy risk.
Extra payment scenarios show interest saved and months shaved off — useful for deciding whether to overpay each month.
Biweekly payment mode demonstrates the compound benefit of paying half each fortnight (effectively 13 monthly payments per year).
Export the full month-by-month schedule as CSV with one click — drop it into Excel, Google Sheets, or your bookkeeping app.
No accounts, no upload, no premium tier. Calculate as many scenarios as you want.

Frequently Asked Questions

How are the monthly payments calculated?

We use the standard amortization formula: M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where P is principal, r is the monthly interest rate, and n is total months. This is the same formula every bank, mortgage lender, and finance textbook uses.

Are the calculations accurate enough to use with my bank?

The math itself is exact for the inputs you provide. Real bank quotes may differ slightly because of: closing costs added to principal, points, varying first-month interest, or different compounding conventions. Use this tool for planning and what-if scenarios; verify final numbers with your lender’s official quote.

Does this calculator support adjustable-rate (ARM) loans?

The current build assumes a fixed rate for the full term. ARM loans require modeling rate adjustments at specified intervals — we’re adding this in a future update. For fixed-rate mortgages, auto loans, personal loans, and student loans, the math is exact.

How do extra payments save interest?

Each extra dollar applied to principal shrinks the balance the next month’s interest accrues against. Over a 30-year mortgage, even $100/month extra can save tens of thousands in interest and shave 4–6 years off the payoff date. The savings panel quantifies this for your specific loan.

Is my financial data sent anywhere?

No. The calculator runs entirely in JavaScript in your browser. Open DevTools → Network when you click Calculate — zero outgoing requests. Your loan amounts, rates, and personal financial details never leave your device.

Why is biweekly payoff faster than monthly?

With biweekly payments at half the monthly amount, you make 26 half-payments per year — equivalent to 13 monthly payments instead of 12. That extra payment goes entirely to principal. Over a 30-year mortgage this typically saves 4–7 years and tens of thousands in interest.

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