Ideal weight calculator
A span you can land anywhere in — because biology offers a range and only calculators offer a single number.
How this is calculated
min = 18.5 × height(m)² max = 24.9 × height(m)²
It is the healthy BMI band, read backwards. That makes it as coarse as BMI itself — it cannot see muscle either — but it has one honest advantage over the classic formulas: it never pretends to a precision it doesn't have.
Why the old formulas are shown, greyed
The Devine figure is displayed for comparison, not as advice. It comes from a 1974 paper about drug dosing, was never validated as a healthy body weight, and skews low for shorter people — often below the healthy BMI band entirely. If it disagrees with the range above, trust the range.
These are the same numbers and the same guards the Talk2Fit app applies when it builds your plan — the calculator is the app's own arithmetic, not a separate approximation.
Questions
Why don't you give me one number?
Because there isn't one. Two people of the same height can both be healthy ten kilograms apart, depending on frame, muscle and where they carry fat. Publishing a single figure invents precision that no evidence supports — and gives people a target to fail at by half a kilo.
What about the Devine or Robinson formulas?
Devine (1974) was designed to scale drug doses by height, not to tell anyone what to weigh; Robinson, Miller and Hamwi are variations on the same idea. They persist because they are simple and old. They also punish short people: for someone of 155 cm they return figures well under a healthy BMI.
Is the top of the range 'fine' then?
For most people, yes — the normal BMI band is wide on purpose. If you sit near the upper edge with a lot of muscle, the number means even less; if you sit there with a large waist, the waist is the thing worth watching, not the total.
Which end should I aim for?
The one you can hold without your life rearranging itself around it. A weight you reach and keep beats a lower one you visit for a fortnight — and the range exists precisely so you have somewhere sensible to land.