Search for your ideal weight and you will find a single confident number. Run three well-known formulas on the same person and you get three different answers. That spread is the most useful thing to understand before you take any of them seriously.
The three formulas
All three start from a base weight for 5 feet (152.4 cm) and add a fixed amount for every inch above it. The Ideal Weight Calculator shows all three side by side:
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50 kg + 2.3 kg per inch | 45.5 kg + 2.3 kg per inch |
| Robinson (1983) | 52 kg + 1.9 kg per inch | 49 kg + 1.7 kg per inch |
| Miller (1983) | 56.2 kg + 1.41 kg per inch | 53.1 kg + 1.36 kg per inch |
The Devine formula was originally written to help estimate drug doses, which is why it is so widely quoted in clinical settings. None of the three was designed as a target for how anyone should look or feel. A historical review found that the equations trace back to insurance-style height and weight tables whose weights were linked to mortality, and that the three formulas give similar answers because they come from the same tables (Pai and Paloucek, 2000).
How the results compare
A woman who is 165 cm (about 65 in) tall gets 56.9 kg from Devine, 57.4 kg from Robinson and 59.8 kg from Miller. A man who is 175 cm tall gets 70.5, 68.9 and 68.7 kg. The formulas agree to within a couple of kilograms in these cases but can drift further apart for very tall or very short people, because they increase at different rates per inch. The formulas were written for heights above 5 feet. Below that, the calculator returns the base weight, which can overstate a healthy weight for much shorter adults, so use the BMI range and a doctor’s advice instead of these figures if you are under 5 feet (152.4 cm).
Using the calculator
- Enter your height in centimetres and choose the sex the formulas should use.
- Read the three results and note the spread rather than picking the one you like best.
- Compare them with the BMI range for your height. For 165 cm, the WHO’s normal BMI band of 18.5 to 24.9 corresponds to roughly 50 to 68 kg.
Why a range beats a number
Body frame, muscle, age and ethnicity all move the weight at which a person is healthy. A 17 kg-wide BMI range for one height is not vagueness; it reflects how much healthy bodies differ. These formulas also ignore body composition entirely, so an athlete may sit well above “ideal” without any health concern.
The formulas are for adults. For children and teenagers, growth charts read by a paediatrician are the right tool. If you are trying to gain or lose weight for health reasons, talk to a doctor or registered dietitian instead of aiming at a formula.
Frequently asked questions
Is ideal weight the same as a healthy BMI?
No. Ideal weight formulas give a single figure from height and sex. A healthy BMI is a range, and neither accounts for muscle, frame or age. If the two disagree, trust the range and your doctor over the single number.
Can I use these formulas when pregnant?
No. Weight changes during pregnancy are expected and individual. Follow the guidance of your midwife or doctor.
Do the formulas apply to athletes?
Not well. A muscular person can weigh well above the result and be perfectly healthy, because the formulas ignore body composition.
Sources: Pai MP, Paloucek FP. The origin of the “ideal” body weight equations. Ann Pharmacother 2000;34(9):1066–1069 (PubMed), which covers the Devine (1974), Robinson (1983) and Miller (1983) equations; WHO BMI categories. General information only, not medical advice.