Ideal weight
Four formulas, four different answers, and an honest account of where they came from — which is drug dosing and insurance tables, not health.
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the number worth using
The four formulas are fitted to height alone. They know nothing about your frame, your muscle, your age or your ancestry, and they give one answer per height rather than a range — which is the main reason not to lean on them.
Where these formulas actually came from
This is the part almost no calculator tells you. The Devine formula was published in 1974, and not to tell anyone what to weigh — it was written to size doses of gentamicin, an antibiotic whose distribution depends on lean mass rather than total weight. It needed a quick estimate of lean body size from height. It worked well enough for that, and then escaped into general use.
Robinson, Miller and Hamwi are refits of the same idea, and later analysis found them closely related to the Metropolitan Life insurance height-and-weight tables — which were built from actuarial mortality data on people who bought life insurance in mid-century America. So the lineage of "ideal body weight" is pharmacokinetics and insurance underwriting. It was never a health target, and it has never been validated as one.
Why four formulas give four answers
Each was fitted to a different sample with a different method, and they disagree by several kilograms at the same height — which is a lot, given they all claim to describe the same thing. The spread is shown above for your height, and it widens as you get taller: around three kilograms at 175 cm, closer to eleven at 190 cm. Hamwi is the oldest and climbs fastest with height; Miller is the flattest. Near five feet they converge, and below it they break down.
They also all begin at five feet, with a constant added per inch above it. Below 152 cm every one of them is an extrapolation past its own data, and they start producing figures nobody should act on. This page suppresses them below that height and shows only the range.
A healthy range beats a single number
The headline here is the weight range corresponding to a BMI of 18.5 to 24.9 for your height, and it is the figure worth using. Not because BMI is a good measure of an individual — it is not, and the BMI calculator is blunt about why — but because a range is the honest shape of the answer. There is no single correct weight for a height. There is a band within which, for most people, weight is not the thing to worry about.
How ancestry changes the range
At the same BMI, people of South Asian, Chinese and South-East Asian descent tend to carry more body fat and develop cardiometabolic disease at lower weights. The WHO sets public-health action points at 23 rather than 25, and NICE carries the same adjustment. Switch the cut-offs above and the healthy range narrows accordingly. None of the four formulas makes any such adjustment at all.
Turning a target into a plan
If you have entered your current weight, the page shows the gap to the nearest edge of the healthy range. To find out what reaching it would involve, thedeficit calculator turns it into a daily intake and the goal date calculator into a date.
A note worth stating plainly: a target below the healthy range is not a goal this site will help you plan, and if you are drawn to one, that is worth talking to someone about. In the UK, Beat runs a helpline on 0808 801 0677. None of these formulas applies in pregnancy, to children, to athletes carrying substantial muscle, or to amputees.