How we check our sums

Free UK health calculators that answer everyday questions in the units you already use, with the working shown and the source linked. Each one goes through the same five checks.

1Plain wordsResults are described plainly. Bodies come in all shapes.
2Real sourcesEvery number comes from the NHS, NICE, the UK Chief Medical Officers or SACN, and we link to them.
3Private by designThe sums happen on your device. Nothing you type is sent or saved.
4Someone to talk toA number is only a start. Your GP, a pharmacist or NHS 111 can help with the rest.

Who we are

Health Calculators is run by R&B Digital Ltd, a small UK company that also makes Tax Calculators and Retirement Calculators. We build tools we would want to use ourselves: quick, plain and honest about what a number can and cannot tell you.

We are not doctors, so we lean hard on the people who are. Every number comes from UK guidance, and every page says where. To see how it works, try the BMI calculator, the sleep calculator or the due date calculator, or browse food and drink.

What we will never do

  • No weight loss targets for anyone under 18, in pregnancy, while breastfeeding or with a BMI under 18.5.
  • Never below a safe floor. Calorie numbers never go below your resting energy, 1,200 kcal, or 1,500 kcal for men.
  • No tracking. Your numbers stay on your device. No accounts, no ads, no selling data.
  • No diagnosis. We explain numbers. Your GP, midwife, pharmacist or dietitian knows you.

Behind the scenes

How a calculator gets made

Five steps, every time, before anything goes live.

  1. 1Find the guidanceWe start with the NHS, NICE, the UK Chief Medical Officers, SACN or peer reviewed research. If there is no good source, we do not build it.
  2. 2Write the sums, then test themEvery formula lives in one place with its source next to it, and has tests with worked examples checked by hand.
  3. 3Show the workingEach page shows the formula, a worked example and what the number can and cannot tell you.
  4. 4Read it for kindnessWe check every line for shaming, diet talk and scare tactics, and take them out. Sensitive topics always point to a GP, midwife or helpline.
  5. 5Check it againPages carry a last checked date. If guidance changes, the number changes in one place and every page updates.

Sources

Who we listen to

Every page was last checked on 21 October 2026. If guidance changes, the sums change in one place and every page updates.

Spotted a mistake?

Tell us and we will fix it, and say so on the page. Corrections are logged with the date, so you can see what changed and why.

Email hello@healthcalculators.co.uk, or see the corrections page for what helps. Ideas for new calculators are welcome on our contact page. How we write and source pages is in our editorial policy and sources policy.

We read everything, but we cannot give personal medical advice. For that, your GP or a pharmacist is the right person.

Information, not advice

Our calculators give general guidance for adults unless a page says otherwise. They cannot diagnose anything and they do not know your history. If you are worried about your health, speak to your GP or call NHS 111. In an emergency, call 999.