Unkillable Tools / Calculator / Loan & mortgage payment calculator
A proper amortisation calculator, verified against the standard reference figures, that you can put on your own site without renting it monthly.
Verified: $300,000 at 6.5% over 30 years gives $1,896.20 a month.
Change the rates, the labels and the maths to match your business, then export it as a single HTML file you paste into your site. Free, no account, and it keeps working whatever happens to us.
Open the builderThe standard amortisation formula is M = P·r·(1+r)ⁿ / ((1+r)ⁿ − 1), where r is the monthly rate and n the number of payments. Building it in one line is painful, so the calculator splits it into named derived values — monthly rate, payment count, compound factor — and composes them.
That structure is worth copying for any multi-step calculation. It's readable six months later, and each intermediate value can be checked on its own.
The engine behind this ships with an automated test suite, and the loan template is asserted against the known reference figure above on every build. Financial calculators that quietly disagree with a bank's own numbers do real damage to trust.
Mortgage brokers, credit unions, car dealerships, equipment finance, solar installers and anyone selling something people finance. The calculator does two jobs at once: it answers the affordability question, and it anchors the conversation on the monthly figure rather than the sticker price.
Because the export makes no network requests, it also passes the security review at institutions where third-party script tags do not — which matters a great deal in financial services.
A payment calculator is a maths tool, not a quote and not financial advice. Depending on your jurisdiction and sector, showing figures like APR or affordability may carry disclosure obligations.
Use the note field under each result to carry your required wording, and check the rules that apply to you. That responsibility sits with the publisher, which is you.
The template includes an extra monthly payment field that adds to the displayed payment. Full amortisation-schedule modelling of early payoff is beyond a single-figure calculator.
Yes — set the symbol on each result. Any symbol works.
It's total payments minus principal for the scheduled term. It excludes fees, insurance, tax and escrow, and the template says so in the note.
Hosted calculator builders charge $5–$115 a month and stop rendering when you exceed your monthly impressions. This one exports a file that runs on your own site and cannot be switched off.
Build one free