BMI calculator

Ten seconds to find out whether this is even for you.

Most people put off asking because they are braced for a lecture. There is no lecture here — just the one number a doctor is obliged to check, what it means, and an honest answer about whether treatment is on the table. Nothing you type leaves your phone.

HeightWeightkilograms

I have a weight-related conditionRaised blood pressure, type 2 diabetes, sleep apnoea, fatty liver or PCOS. It lowers the prescribing threshold from 30 to 27.

—Your number appears here the moment you type. It is not sent anywhere, not stored, and not attached to your name — this whole thing runs in your browser.

Where BMI is wrong

One number that ignores most of you

If your number came back higher than you hoped, read this before you take it personally. We use BMI because prescribing thresholds are written in it. That is the only reason. Your doctor reads your waist, your blood pressure and your history alongside it, and any of those can overrule it.

It cannot tell muscle from fat

A heavily trained person can land in the obese range on BMI alone. Nobody is going to prescribe them a GLP-1 on that basis.

It ignores where the fat sits

Visceral fat around the organs carries far more risk than the same weight on the hips. A tape measure round your waist catches what BMI misses.

It was built on a European population

Cardiometabolic risk rises at lower BMI in South Asian and some African populations, which is why a doctor reads the whole picture rather than the one figure.

It says nothing about direction

A BMI of 29 that was 24 last year is a completely different conversation from a BMI of 29 that has not moved in a decade. The trend matters more than the point.

This calculator is a screening aid, not a diagnosis and not a prescribing decision. It is not suitable for anyone under 18, pregnant or breastfeeding. Nothing you type is transmitted or stored.

You know the number. Now find out what a doctor says.

The health form asks the things BMI leaves out — your history, your medication, what you have already tried and how it went. Three minutes, read the same day, and free if the answer turns out to be no.

Start free consultation Read the questions first

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