Ideal Weight Calculator
Experts have chased a formula for ideal body weight (IBW) for decades, and several survive side by side. This calculator runs the four classics — Robinson, Miller, Devine, and Hamwi — on your height, gender, and age, and puts them next to the healthy BMI range so you can compare instead of trusting any single number.
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How much should I weigh?
Almost everyone has tried to lose weight, or watched someone do it — usually chasing an "ideal" number absorbed from screens and magazines. The irony is that ideal body weight was invented for none of that: it began as a dosing tool, because many drugs are metabolized in proportion to IBW rather than total weight, and it later spread into sport, where weight classes need a reference. Nothing in the formulas knows what you look like.
So hold the result at arm's length. IBW counts height and gender only — no muscle, no fat distribution, no frame. A lean, heavily trained athlete can sit well above every formula's output in perfect health, and someone can sit exactly on it in poor health. No index — IBW, BMI, or any other — can certify how much a specific person should weigh. They are references; the healthy habits (moving regularly, eating mostly unprocessed food, sleeping enough) matter more than landing on a number.
The factors behind the number
Age — After the growth years (about 14–15 for girls, 16–17 for boys), age alone shouldn't move IBW much — but people do shrink (roughly 1.5 inches for men, 2 for women by age 70) and trade muscle for fat as they age, which is why the healthy range for children and teens is read off CDC growth charts instead.
Gender — Women naturally carry a higher share of body fat, have lighter bones, and are on average shorter; men carry more muscle, and muscle is heavier than fat.
Height — Taller bodies hold more of everything. A man typically weighs 10–20% more than a woman of the same height.
Body frame size — Bone structure matters: a large-framed person weighs more at the same height, in health. Frame is usually judged by wrist circumference against height:
Women
- Under 5'2": small < 5.5", medium 5.5–5.75", large > 5.75"
- 5'2" – 5'5": small < 6", medium 6–6.25", large > 6.25"
- Over 5'5": small < 6.25", medium 6.25–6.5", large > 6.5"
Men (over 5'5")
- Small boned: wrist 5.5–6.5"
- Medium boned: wrist 6.5–7.5"
- Large boned: wrist over 7.5"
The four formulas
Every IBW formula shares one shape: a base weight at exactly 5 feet, plus a fixed increment for each inch above it. A 5'10" man under Devine, for instance, gets 50 + 2.3 × 10 = 73 kg (about 161 lbs). The formulas differ only in the base and the increment — a fingerprint of whoever fitted them, and when.
G. J. Hamwi (1964)
Men: 48.0 kg + 2.7 kg per inch over 5 feet
Women: 45.5 kg + 2.2 kg per inch over 5 feet
Invented for medicinal dosage purposes — the original.
B. J. Devine (1974)
Men: 50.0 kg + 2.3 kg per inch over 5 feet
Women: 45.5 kg + 2.3 kg per inch over 5 feet
Also born in dosing, and now the most widely used of the four.
J. D. Robinson (1983)
Men: 52 kg + 1.9 kg per inch over 5 feet
Women: 49 kg + 1.7 kg per inch over 5 feet
A 1983 modification of the Devine formula.
D. R. Miller (1983)
Men: 56.2 kg + 1.41 kg per inch over 5 feet
Women: 53.1 kg + 1.36 kg per inch over 5 feet
The other 1983 modification of Devine — note the higher base and gentler slope.
Alongside them, the healthy BMI range: the WHO's 18.5–25 band, turned into weights for your height. For children and teens the equivalent is not a fixed band at all — the CDC asks that children sit between the 5th and 85th BMI percentiles for their age, which is what this calculator reports up to age 20 (and why younger children get the CDC sentence instead of a formula table: the formulas are adult tools, anchored at 5 feet).
Limitations
Formulas built to fit as many people as possible cannot be precise for any one person. They ignore disabilities, extremes of height and build, activity level, and body composition entirely. Use this page as a general guideline drawn from popular formulas — not as a strict value you must hit to earn the word "ideal."
FAQ
Which formula should I believe?
Devine is the most widely used, but the honest answer is the zone: where the four formulas and the healthy BMI range overlap is a reasonable neighborhood for a typical body. Outside it, the other factors — muscle, frame, fat distribution — decide.
Can I be healthy above my ideal weight?
Yes — athletes prove it constantly. The formulas cannot see muscle. If your body fat percentage is in a healthy band, a high IBW comparison is mostly a compliment to your training.
Why did I get a sentence instead of the table?
The formulas are anchored at 5 feet, so at heights of 5 feet or below the calculator reports the healthy range directly — the WHO range for adults, the CDC range for ages 2–20.