Free ideal weight calculator
Four formulas, four answers, one honest range.
Devine, Robinson, Miller and Hamwi all claim to give your ideal weight, and they disagree — often by five kilos or more on the same body. So this page prints all four, plus the healthy BMI range for your height, which is wider and considerably more defensible than any of them.
General wellness guidance, not medical advice. If you are pregnant, breastfeeding, under 18, or managing a medical condition, talk to a doctor or a registered dietitian before acting on any of these numbers.
Where these formulas actually came from
| Formula | Year | Written for |
|---|---|---|
| Hamwi | 1964 | Estimating nutritional needs in clinical practice |
| Devine | 1974 | Calculating drug doses — still the clinical default for that |
| Robinson | 1983 | A revision of Devine against different data |
| Miller | 1983 | Another revision, flatter as height increases |
Not one of them was designed to tell a person what they should weigh. They were built to standardise a dose or a clinical estimate, they take height and sex and nothing else, and they have been repurposed by the internet into something they were never validated for.
What to use instead
Three things, in increasing order of usefulness. The healthy BMI range for your height, which is a band rather than a point. Waist-to-height ratio kept under 0.5, which needs only a tape and tracks the fat that actually matters metabolically. And body fat percentage, which is the only one of the three that can tell muscle from fat — the thing every height-based formula is blind to.
If the gap between where you are and where you want to be is real, size it deliberately: the deficit calculator turns it into a weekly rate and a date, and the protein calculator covers the part that decides whether the weight you lose is fat or muscle.
Common questions
What is my ideal weight for my height?
There is no single answer, and any page that gives you one is hiding the disagreement. The four published formulas above — Devine, Robinson, Miller and Hamwi — routinely differ by five kilos or more for the same person, because they were fitted for different purposes decades apart. The healthy BMI range for your height is wider and more defensible than any of them.
Where do these formulas come from?
Devine (1974) was written for calculating drug doses, not for body image, and it is still the clinical default for exactly that. Robinson (1983) and Miller (1983) are later revisions fitted to different data. Hamwi (1964) is the oldest and the most generous as height increases. None of them was ever validated as a health target.
Do these account for muscle or frame size?
No. Every one of them takes height and sex and nothing else. A heavily trained person and a sedentary person of identical height get an identical "ideal", which is obviously wrong and is the clearest reason to treat the output as a rough band rather than a goal. Body fat percentage answers the question these formulas are pretending to answer.
Should I use ideal weight or BMI?
BMI, if you must pick one — it at least gives you a range rather than a single number, and the range is wide enough to contain normal human variation. Better still is a combination: a healthy BMI band, a waist under half your height, and a body fat percentage in a sensible range for your sex.
Is it healthy to aim for my ideal weight?
Only if it is close to where you already are. Chasing a number from a 1974 dosing formula can mean aiming below your own healthy range, and a goal set that way tends to be reached by methods nobody would recommend. Aim for a weight you can hold with a diet you would be willing to eat for years.
How long would it take to get there?
That depends on the gap and the rate, and the deficit calculator works both out — including the part most calculators skip, which is that maintenance falls as you get lighter, so the finish drifts later than straight-line arithmetic promises.
Other free calculators
A target is a guess. A trend is evidence.
NutriLog AI tracks your weight as a smoothed trend and re-refines the plan around it, instead of holding you to a number a 1974 formula picked. Free, no ads, Android. Free on Google Play.