Ideal Weight Calculator: Devine, Robinson, Miller, and Hamwi Formulas
How much should you weigh? Doctors have asked this question for over a century, producing several respected formulas. This free ideal weight calculator computes all four major ones — Devine, Robinson, Miller, and Hamwi — from your height and sex, averages them, and adds the healthy BMI weight range as an evidence-based reality check.
The Four Classic Formulas
All four share the same structure: a baseline weight at 5 feet, plus a fixed increment per inch above it.
| Formula | Men (at 5'0") | Per inch | Women (at 5'0") | Per inch | |---|---|---|---|---| | Devine (1974) | 50 kg | +2.3 kg | 45.5 kg | +2.3 kg | | Robinson (1983) | 52 kg | +1.9 kg | 49 kg | +1.7 kg | | Miller (1983) | 56.2 kg | +1.41 kg | 53.1 kg | +1.36 kg | | Hamwi (1964) | 48 kg | +2.7 kg | 45.5 kg | +2.2 kg |
The Devine formula was created for medication dosing and remains the clinical standard; Hamwi came from dietetics; Robinson and Miller were later refinements. Notice they disagree by up to 8 kg (18 lb) for the same height — a hint that "ideal" is fuzzier than it sounds.
Worked Example
A 5'8" (173 cm) woman: 8 inches above 5 feet.
- Devine: 45.5 + 2.3 × 8 = 63.9 kg (141 lb)
- Robinson: 49 + 1.7 × 8 = 62.6 kg (138 lb)
- Miller: 53.1 + 1.36 × 8 = 64.0 kg (141 lb)
- Hamwi: 45.5 + 2.2 × 8 = 63.1 kg (139 lb)
Average: ≈ 63.4 kg (140 lb). Her healthy BMI range at 173 cm is 55.3–74.4 kg (122–164 lb) — much wider, and it includes every formula's answer.
Why the BMI Range Matters More Than Any Single Number
The formulas were built on mid-20th-century populations and assume an average frame. They cannot see your muscle mass, bone density, or body composition — which is why two people at the "ideal" 140 lb can look and test completely different. The healthy BMI band (18.5–24.9) spans roughly 40 lb at any height, and that entire band is medically acceptable. Research on longevity finds risk curves are flat across it and only rise sharply at the extremes. Think of the formula average as a landmark and the BMI range as the map.
Adjusting for Your Frame
A practical rule from the original research: people with smaller frames sit near the bottom of their range, larger frames near the top. A quick proxy for frame size — wrap your thumb and middle finger around your opposite wrist:
- Fingers overlap — likely small frame; aim lower in the range
- Fingers just touch — medium frame
- Fingers gap — larger frame; the upper range fits better
Should You Chase Your Ideal Weight?
Only as a directional guide. If you are far from both the formulas and the BMI band, the formulas give you a long-term destination; the smarter play is a 5–10% weight change first, which already improves blood pressure, blood sugar, and cholesterol. Compute the calorie targets for that journey with our TDEE calculator, or check whether your current weight is mostly fat or muscle with the body fat calculator.
Ideal weight formulas are screening estimates for adults, not targets for athletes, pregnant women, or growing teens. Discuss personal targets with a healthcare provider.