Calculators built for the UK, not adapted from somewhere else.

How we build these calculators

Most generic online calculators are built once for a global audience and never account for how the UK actually works — its tax bands, statutory rates, unit conventions and institutions. Ours are built the other way round: we start from the actual UK rules and formulas, then build the calculator around them. A mortgage repayment calculator uses standard UK repayment/interest-only amortisation maths; a salary calculator applies current Income Tax bands and National Insurance thresholds; a stamp duty calculator follows SDLT bands as set out by HM Revenue & Customs (HMRC); a BMI calculator uses the same thresholds referenced by the NHS, including the adjusted bands recommended for some ethnic groups; a road tax estimator reflects DVLA Vehicle Excise Duty bands.

Where a result depends on official rates, bands or thresholds, we reference the government or institutional source it's built from — HMRC and gov.uk for tax, the NHS for health guidance, the DVLA for vehicle rules, the Office for National Statistics (ONS) and Bank of England for economic figures — so you can cross-check anything decision-critical against the primary source. Rates and bands change, most often at the start of a new tax year, so we review and update calculators when official figures change rather than leaving them static.

Every calculator also shows its working — the intermediate numbers, not just a final figure — so you can see exactly how a result was reached instead of trusting a black box. None of this replaces a qualified accountant, financial adviser, GP or structural engineer for decisions that matter; it's built to make everyday numbers faster and clearer to work through, not to replace professional advice.