What an ideal weight calculator actually tells you
An ideal body weight (IBW) calculator estimates a healthy weight for your height and sex using formulas that doctors and pharmacists have relied on for decades. They were originally built to standardise medication dosing and provide a clinical reference point — not to set a rigid target for the bathroom scale. Because no single equation fits everyone, this tool shows you four of the best-known formulas side by side, plus a weight range derived from the healthy BMI band, so you get a realistic spread instead of one falsely precise number.
How the math works
Every formula here uses the same trick: it sets a baseline weight at a height of
5 feet (60 inches) and then adds a fixed number of pounds for each inch above
that. First the tool converts your height to total inches
(inches = cm / 2.54, or feet × 12 + inches), then applies each formula:
- Devine: male
50 + 2.3 × (inches − 60); female45.5 + 2.3 × (inches − 60) - Robinson: male
52 + 1.9 × (inches − 60); female49 + 1.7 × (inches − 60) - Miller: male
56.2 + 1.41 × (inches − 60); female53.1 + 1.36 × (inches − 60) - Hamwi: male
48 + 2.7 × (inches − 60); female45.5 + 2.2 × (inches − 60)
Each result is in kilograms; multiply by 2.20462 to convert to pounds. The healthy
range is separate: it solves the BMI formula for weight at your height, using
weight = BMI × height(m)² with BMI values of 18.5 and 24.9 to give the low and high
ends of the band.
A worked example
Take a man who is 5 ft 10 in tall — that is 70 inches, so
inches − 60 = 10. The Devine formula gives
50 + 2.3 × 10 = 73.0 kg (about 161 lb). Robinson gives
52 + 1.9 × 10 = 71.0 kg, Miller gives 56.2 + 1.41 × 10 = 70.3 kg, and
Hamwi gives 48 + 2.7 × 10 = 75.0 kg. His height of 1.778 m puts the healthy BMI range
at roughly 58.5 kg to 78.7 kg (129–174 lb) — and notice all four formula results sit
comfortably inside it.
Which formula should I use?
Devine (1974)
The most widely used in medicine, especially for drug dosing. A solid, middle-of-the-road default.
Robinson (1983)
A refinement of Devine that tends to return slightly lower weights for the same height.
Miller (1983)
Uses the gentlest per-inch increment, so it usually gives the lowest of the four estimates.
Hamwi (1964)
The oldest formula here and the quickest to compute by hand; it generally reads highest.