About
A calculator we wished existed.
Mortgagemaths is a small, independent tool for working out the numbers behind a UK property purchase. Free, no sign-up, no tracking beyond what advertising requires.
Who runs it
Mortgagemaths is an independent project. If you spot an error or have a question, get in touch — we treat rate accuracy as a priority.
Why we built it
Every calculator we tried either used last year's tax bands, hid its assumptions, or buried the result under a lead-capture form. We wanted something different: the right numbers, shown clearly, with the maths visible so you can check it yourself.
Buying property in the UK is already complicated enough. A calculator should make it simpler, not add to the noise.
Noticed something wrong?
Tax bands change — sometimes mid-year, sometimes with little public fanfare. If you spot a number that looks off, we want to know. Drop us a line at [email protected] and include the source you're checking against (a link to HMRC, Revenue Scotland, or the Welsh Revenue Authority is ideal). We'll confirm and update within 24 hours.
Accuracy matters here. People make real decisions based on these figures. If we've got something wrong, we'd rather fix it fast than have someone budget incorrectly for a purchase.
How we keep the numbers current
All stamp duty bands are maintained in a single rates file, cross-referenced against the three official sources. The version and last-updated date are shown in the footer of every page.
- Stamp duty bands — reviewed against HMRC, Revenue Scotland, and the Welsh Revenue Authority whenever a change is announced.
- Income multiples — 4× single, 4.5× joint reflects typical lender practice. We're upfront that this is indicative: real offers depend on outgoings, credit, and individual lender appetite.
- Repayment maths — standard amortisation formula. The numbers will match any other repayment calculator to the penny.
What we don't do
We don't sell mortgages. We don't run a panel of preferred lenders. The broker referral on each result page goes to a fee-free whole-of-market broker; if you use it and they place a mortgage, they pay us a fixed referral fee — that's how the site stays free.
We don't store anything you type. There's no account, no email capture. The calculators run entirely in your browser.
Get in touch
Questions, corrections, or a calculator you wish existed? Email [email protected] — we read everything and reply within two working days.
Sources
- HMRC — Stamp Duty Land Tax: gov.uk/stamp-duty-land-tax
- Revenue Scotland — LBTT residential rates: revenue.scot
- Welsh Revenue Authority — LTT rates and bands: gov.wales/land-transaction-tax
- Bank of England — base rate history: bankofengland.co.uk