Ideal Weight Calculator

The first version of this tool only showed the Devine formula result, and I got messages within a week from people confused about why a friend using a different app got a different "ideal weight" for the same height. Turns out every formula in this space was built for a different purpose, decades apart, and none of them agree with each other by more than a couple kilos. So instead of picking one and pretending it's authoritative, this calculator runs all of them side by side.

How it works

Devine (1974) was designed for calculating drug dosages, not fitness — it's still the one most doctors default to because it's what shows up in clinical references. Robinson and Miller (both 1983) are adjustments of Devine using different reference populations, and tend to land a bit lighter or heavier respectively. Hamwi (1964) is the oldest of the bunch and generally produces the lowest number of the group. Alongside those four, the calculator also shows the WHO healthy-BMI-range approach, which isn't a single number at all — it's a band (18.5 to 24.9 BMI) converted into a weight range for your height. All five numbers get computed from the same height and sex inputs; nothing here is doing anything more sophisticated than the classic per-inch-over-5-feet math each formula defines.

A real example

For a 5'8" (173cm) man, the five results typically land like this: Hamwi ≈ 68.9kg, Robinson ≈ 68.9kg, Devine ≈ 70.7kg, Miller ≈ 71.7kg, and the WHO healthy-BMI range spans roughly 55.4–74.5kg. Notice all four formula results fall comfortably inside the WHO range — that's usually the case, and it's a decent sanity check. If a formula result falls outside your BMI range, height entry errors are the most common cause, so double-check units first.

Where this gets misused

• Treating any single number as a target to hit exactly. These are population averages from small, dated reference groups (the original Devine/Hamwi studies were done on a few hundred people, decades before modern body composition science). A 5kg spread between formulas for the same height should tell you the "right" answer is a range, not a number on a scale.
• Ignoring that none of these account for muscle mass. An athlete with real muscle can be 15kg over every formula here and be in great health; someone sedentary can hit the "ideal" number and still have poor metabolic markers. If you lift weights or do any serious strength training, weigh these results a lot less than waist circumference or body fat percentage.
• Using this instead of talking to an actual clinician for anything medical. If you're asking because of a health condition, medication dosing, or an eating disorder history, this tool is not the right resource — it's a general-population estimate, not medical advice, and I'd rather say that plainly than have someone lean on it for something it wasn't built for.