What we do
Health numbers – BMI, healthy weight, blood pressure, centiles, heart risk – can be confusing. We build simple calculators that use the same formulas and thresholds as UK health services, and we explain the results in clear language, with honest information about what each number can and cannot tell you.
- UK units throughout: stones and pounds, feet and inches, as well as kilograms and centimetres.
- UK guidance first: NHS, NICE, RCPCH and other recognised UK sources.
- Private by design: calculators run in your browser and we never see what you enter.
- Free, with no sign-up.
Who writes our content
Our content is produced by the BMI Calculator NHS Editorial Team, a small team of health writers and web developers based in the UK and abroad. Every page is researched from primary sources – the NHS website, NICE guidelines, peer-reviewed research and official statistics – and checked against those sources before it is published.
We do not give personal medical advice. Our role is to make reliable public guidance easier to find, understand and use. Read how we work in our editorial policy.
How our calculators work
Adult BMI and weight
NHS/NICE NG246 BMI categories, including lower thresholds for South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean adults.
Child growth
UK-WHO growth references (WHO 2006 standards and the UK 1990 reference), using the LMS method used on RCPCH charts.
Heart risk
The QRISK3-2017 algorithm released by ClinRisk Ltd under the GNU LGPL, with unchanged coefficients.
Blood pressure
NHS ranges and NICE NG136 thresholds for clinic and home readings.
Each tool page includes a “How this tool works” section listing the formula or reference used, and a full source list.
Independence and funding
bmicalculatornhs.net is not part of, endorsed by or affiliated with the NHS, NHS England, NICE or any government body. “NHS” in our name describes the guidance our tools are based on. The site is funded by advertising. Advertisers have no influence over our content, and we do not accept payment for health claims or reviews.
Contact
Found a mistake or have a question? Email info@bmicalculatornhs.net or use our contact page. For urgent medical advice call NHS 111, or 999 in an emergency.
Last updated: 27 October 2026