Where these formulas come from
None of them started as health advice. Devine (1974) was created to dose medication; Hamwi (1964) for quick clinical estimates; Robinson and Miller (1983) refined Devine against actuarial data. They survive because they are simple and broadly sensible — but the spread between them for the same height is a useful reminder that "ideal" was never a single number.
Why the BMI range is the headline
The 18.5–25 BMI band is the only one of these measures tied to modern outcome data, and it is honest about being a range: for someone 178 cm tall it spans nearly twenty kilograms. Where you personally sit well inside that band depends on frame and muscle — an athlete can be healthy above it, which is BMI's known blind spot.
A better question than "what should I weigh"
Waist circumference and body fat percentage track health risk better than scale weight, because they see where the weight is. If you are near the top of the BMI band, our body fat calculator is the more informative next step than any ideal-weight formula.
Frequently asked questions
The four formulas disagree — which is right?
None of them is "right"; they are different fits from different decades. Their spread is roughly the honest uncertainty. Use the BMI range as the anchor and the formulas as reference points.
Does age matter for ideal weight?
The classic formulas ignore age by design. In practice slightly higher BMI in older adults is not associated with worse outcomes, so the band is if anything more forgiving with age, not less.
Is this medical advice?
No. The Devine, Robinson, Miller and Hamwi formulas, which disagree with each other by several kilos. None of these formulas knows anything about your build, and a doctor does.
Is my data stored or sent anywhere?
No. Your height and weight are not sent anywhere.
Something wrong with this tool, or an idea for it? Tell us