If you run an estate agency, a mortgage brokerage or any UK property or finance site, a stamp duty calculator is one of those tools your visitors quietly expect to find. Someone weighing up a purchase wants to know what they'll actually pay — and if your site answers that, they stay on your site instead of drifting off to a portal.
Building one isn't hard. The part nobody warns you about is keeping it correct — and that's where most calculators quietly fail.
Why "correct" is the whole game: on 1 April 2025 the SDLT nil-rate band dropped from £250,000 back to £125,000. Overnight, a £250,000 purchase went from a £0 stamp duty bill to £2,500. Any calculator built before that date and not updated since now tells every buyer the wrong number — and they're making a real decision on it.
The three ways to add a stamp duty calculator
1. Build your own
A developer can put a stamp duty calculator together in a day or two — a few input fields, the band logic, a result. The build is the cheap part. The expensive part arrives at every Budget, when the rates change and someone has to remember to open the code, update the bands, re-test it and redeploy. Miss it, and your calculator carries on confidently handing out figures that are now wrong. April 2025 is the perfect example: a calculator still using the old £250,000 nil band tells someone their £250,000 flat is stamp-duty-free, when it now costs them £2,500.
2. Drop in a free plugin or widget
Faster than building from scratch — search "stamp duty calculator plugin" and you'll find a handful. The catch is maintenance and trust. Plenty were last updated years ago (it's easy to find SDLT plugins still pinned to 2022 rules), they rarely match your branding, and you're handing a third party you've never spoken to responsibility for a number your buyers act on. A free plugin that's gone stale is arguably worse than no calculator — it's wrong, with confidence.
3. Embed a maintained one
The third option is to embed a calculator that someone else keeps current for you, centrally. You paste one line of code once; when the rates change in a Budget, they're updated at the source and your embedded calculator is correct the same day — you never touch it. That's the model we built WealthR's calculators on, precisely because the maintenance is the real cost, not the build.
The calculator isn't the product. "You never have to touch it again after the next Budget" is the product.
The hidden cost is maintenance, not the build
UK stamp duty has moved repeatedly in recent years — thresholds shifted in 2022, the nil band and first-time-buyer relief both changed in April 2025, and the additional-property surcharge rose to 5%. Each move is a small job if you remember it and a silent liability if you don't. For most firms, "remember to re-code the calculator after every fiscal event" isn't a job anyone actually owns — which is how calculators drift out of date without anyone noticing, until a buyer or a compliance check catches it.
A quick, honest comparison
| Build your own | Free plugin | Maintained embed | |
|---|---|---|---|
| Setup effort | 1–2 dev days | ~1 hour | ~5 minutes |
| Stays correct after a Budget | Only if you remember | Often not | Yes, centrally |
| Mobile-friendly | Depends on the build | Varies | Yes |
| Your branding | Yes | Rarely | Yes (white-label) |
| Ongoing cost | Dev time each change | £0 (but stale) | Free, or £19/mo white-label |
How to embed one in about five minutes
If you go the embed route, adding it is genuinely a copy-paste job. You pick a calculator, copy a one-line snippet, and paste it into any page, CMS block or intranet page. It loads in an iframe, resizes itself to fit, and works on WordPress, Squarespace, Wix, a hand-built site or a SharePoint intranet — anywhere HTML goes. The snippet looks like this:
<iframe src="https://wealthr.co.uk/tools/stamp-duty-calculator-uk/?embed=1" style="width:100%;border:0;height:720px" loading="lazy" title="UK Stamp Duty Calculator by WealthR"></iframe>
That's it. No account needed for the free version — you keep a small "Powered by WealthR" link, and the calculator stays current on its own. If you'd rather it carried only your branding with no link, that's the white-label option.
Grab the embed code for your site
Pick a calculator — stamp duty, salary sacrifice, pension, compound interest — copy the snippet, and paste it into your site or intranet. Free to embed with a link back, or white-label it in your own branding from £19/month, updates included.
Get your embed code →The honest bottom line
Any of the three routes can put a stamp duty calculator on your site today. The question that actually matters is what happens at the next Budget. If the answer is "someone on our team will remember to re-code it," building your own is fine. If it isn't — and for most firms it honestly isn't — embedding a maintained calculator is the cheaper, safer way to make sure the number your buyers see is the number they'll actually pay.
Frequently asked
How do I add a stamp duty calculator to my website?
Is it free to embed a stamp duty calculator?
Will the calculator stay correct after the Budget?
Can I put my own branding on it?
Does it work on WordPress, Squarespace or an intranet?
General information for UK businesses, not tax or financial advice. SDLT figures are for England & Northern Ireland from 1 April 2025 and can change at any fiscal event; Scotland (LBTT) and Wales (LTT) use different rates. Always confirm current thresholds before relying on a figure.