Last updated 21 October 2026
What our calculators are for
They give general estimates and explanations in the units people in the UK use. They are not a diagnosis, treatment plan, prescription or emergency service.
How we sort tools
- Fun and lifestyle: lighter tools, with clear limits.
- Fitness: training and performance estimates, with injury common sense.
- General health: everyday measures such as BMI or calories, with NHS or GOV.UK links.
- Sensitive health: pregnancy, cycles, alcohol and eating. A calmer tone, stronger signposting, and the Beat helpline on eating topics.
- Clinical explainers: results from tests. Neutral language, and never a change to treatment from the page.
How a page is checked
Each formula sits in one place beside its source and has tests with hand worked examples. Every page shows the working, says what the number cannot tell you, and carries a last checked date. We revisit pages when NHS, NICE or GOV.UK guidance changes, or when someone reports a problem. More on how we check our sums.
Who writes it
Pages are written and checked by the R&B Digital team. We do not invent named clinicians or reviewers. If a page gains an independent clinical review, it will say so clearly, with the reviewer's name.
Tone
Plain British English, clear and factual. No scare tactics, no shaming, no "safe to drive" style promises and no gamifying unhealthy goals. No weight loss targets for anyone under 18, in pregnancy or with a low BMI.