About this site
A set of weight-loss calculators built for the UK, with the workings shown.
Updated
Weight Loss Calculator exists to answer one question properly: how much weight do you want to lose, roughly how long could it take, and which numbers actually drive that?
Built for the way people here actually talk about weight
Most weight-loss calculators are built around American conventions. If you think in stone and pounds, they make you convert first. Every tool here takes stone and pounds directly, and you can switch to kilograms or pounds at any point without re-entering anything.
What we do differently
- We show a range, not a date. The underlying estimates do not support more precision than that, and pretending otherwise would be dishonest.
- We model your energy needs falling as you lose weight, rather than dividing by a fixed number and calling it an answer.
- We publish every formula and assumption, including the ones we are not confident about.
- We will not produce a plan for a target below the healthy BMI range, however it was arrived at.
- Your measurements never leave your device.
What this site is not
It is not a diet plan, a clinic, a pharmacy, or a substitute for advice from a professional who knows your history. The calculators produce estimates from population equations. They cannot examine you, and they do not know anything about your health.
How this is funded
The calculators carry no advertising, no paid links and no sponsored content. No calculator on this site links to a provider that pays us, and none of them changes what it says based on who does.
A price comparison section is being built, and it will be funded differently: some of its outbound links will earn a commission. It is not finished. What is currently in the site runs on invented pharmacies and invented prices, is marked as such on the page, and is kept out of search results. When it lists real prices, ranking will be by total cost to you and nothing else, and every page carrying a paid link will say so on the page.
How the numbers are produced
Every figure on the site comes out of one calculation engine. No page does its own arithmetic, no result is written by hand, and nothing is generated on the fly by a language model. The engine is a set of pure functions: the same inputs always produce the same output, which is what makes the numbers checkable rather than merely plausible.
That engine is covered by a test suite that runs on every change, including cases most calculators get wrong. Converting 76.2 kg has to give 12 st 0 lb and never 11 st 14 lb; 182.8 cm has to give 6 ft 0 in and never 5 ft 12 in; switching between stone and kilograms any number of times has to leave your entry exactly where it started. Those are tested rather than hoped for.
Health figures are held in a single register of sources, each recording where it came from and when it was last checked. Where a figure could not be read at its own source, it is marked as unconfirmed and the methodology page says so rather than presenting it as settled.
Who it is for
Anyone in the UK who wants a straight answer about their own numbers and would rather see the working than be handed a verdict. It assumes no interest in nutrition as a subject, no app, and no account.
Get in touch
If you spot an error, we want to know. See our corrections policy or the contact page.