Free · No signup · One line of HTML

A mortgage calculator for your website that people actually finish using

Drop a fast, mobile-friendly mortgage payment calculator onto any site — WordPress, Webflow, Squarespace, plain HTML — with a single <iframe>. Full PITI breakdown, PMI, extra-payment savings and a year-by-year amortization schedule. Free to use with a small credit link. $39 one-time removes it.

Try it — this is the real widget

Everything below runs entirely in the visitor's browser. No data leaves the page, no cookies, no tracking, nothing to configure.

Live demo — smeltworks.com/loancalc/widget.html

Embed it in one line

Pick your brand colour, copy, paste. That's the whole install.

Want it fully self-hosted instead of iframed from here? Download the source kit — one HTML file, no build step, no dependencies. Upload it anywhere and point the iframe at your own copy.

What it does

Full PITI, not just P&I

Principal, interest, property tax, insurance, HOA and automatic PMI while loan-to-value is above 80% — the number a buyer actually pays.

Extra-payment savings

Type an extra monthly amount and it shows the exact years saved and interest avoided. This is the field that keeps people on the page.

Real amortization schedule

Month-by-month maths rolled up year-by-year, so extra payments are exact rather than approximated by a formula.

Works on a phone

Single-column below 520px, 16px inputs so iOS doesn't zoom, tabular figures, auto-height inside the iframe. ~11KB, no libraries.

Free or licensed

 Free$39 licence
Use on your own site
Full source, self-host it
Custom accent colour
Credit link requiredYesNo
Use on client / commercial sitesWith creditUnlimited
Modify and rebrand the source

Free

$0
  • The complete widget, full source
  • Unlimited pages on your own site
  • Keep the "Calculator by Smeltworks" line visible
  • Can't remove the credit
Download free kit

Commercial licence

$39 one-time
  • Everything in free
  • Credit link removed — add &credit=0
  • Unlimited client sites, forever
  • Rebrand, restyle, ship it inside your product
  • Your Stripe receipt is your licence — nothing to wait for
Buy the licence — $39

Questions

Do I get the file straight away?

Yes — the download link above is the complete kit and it is not gated. The $39 doesn't buy a secret file; it buys the right to run it without the credit link. Buy it and the Stripe receipt in your inbox is your proof of licence.

Why sell it this way?

Because a calculator hidden behind a checkout helps nobody. Bloggers and hobby sites should just use it. Mortgage brokers and agencies building client sites can't put someone else's link on a client page — that's who the licence is for.

Does it send data anywhere?

No. It's one HTML file with inline JavaScript, no network calls, no analytics, no cookies. Nothing a visitor types leaves their browser.

Will it match my site?

Pass any hex colour as ?accent=. If you self-host the kit, the whole palette is CSS custom properties at the top of the file — change five lines.

Is the maths right?

Standard amortizing-loan formula for the payment, then a real month-by-month loop for the schedule and extra-payment results. PMI is estimated at 0.55%/yr of the loan while LTV is over 80% — a US market average, so treat it as an estimate, and it disappears once the down payment reaches 20%.