Ideal Weight Calculator
Healthy weight range from height and sex using Robinson and Devine formulas.
What it does
Doctors once dosed drugs and judged builds with height weight tables, and two formulas survived that era. Robinson (1983) and Devine (1974) each set a base weight at five feet and add a fixed amount per inch above, with different bases for men and women.
The tool above runs both from height and sex in metric or imperial. It returns each estimate plus the span between them as a target zone.
These lines describe medium frames. Large boned people sit healthily above them and small frames below, which is why the span matters more than either single number. Muscle shifts athletes further still.
Modern practice pairs ideal weight with BMI and waist measures rather than trusting one line. A weight inside the span with a healthy waist and BMI near 22 is a strong place to stand.
How to use
- Switch the unit system first: metric for cm and kg, imperial for inches and pounds.
- Pick sex and enter morning height without shoes.
- Read both formulas, then aim inside the span.
- Recheck with BMI and waist before judging the number.
Formula
- 52 / 49 / 50 / 45.5
- Base kg at exactly 5 feet, per formula and sex.
- in - 60
- Inches above five feet. Below five feet the term subtracts.
- 1.9 / 1.7 / 2.3
- Kg added per inch above five feet.
Devine was built for drug dosing and runs slightly heavier than Robinson. Hamwi and Miller variants exist with nearby constants; all four agree within a few kilos for average heights.
Worked example
Example: man, 178 cm
Male, 178 cm tall, which is 70.08 inches.
- Inches over five feet: 70.08 - 60 = 10.08.
- Robinson: 52 + 1.9 x 10.08 = 52 + 19.15 = 71.1 kg.
- Devine: 50 + 2.3 x 10.08 = 50 + 23.18 = 73.2 kg.
- Span: 71.1 to 73.2 kg. In pounds that is 156.9 to 161.3.
Reference table
| Height | Robinson | Devine |
|---|---|---|
| 165 cm (5ft 5in) | 61.4 kg | 61.4 kg |
| 170 cm (5ft 7in) | 65.2 kg | 65.9 kg |
| 175 cm (5ft 9in) | 68.9 kg | 70.5 kg |
| 180 cm (5ft 11in) | 72.6 kg | 75.0 kg |
| 185 cm (6ft 1in) | 76.4 kg | 79.5 kg |
Limits
- Medium frames assumed. Bone structure shifts healthy weight.
- Muscle is not counted. Athletes read heavy.
- Below five feet the lines extrapolate thinly.
- Elderly, ill, and growing teens need clinical judgment.
Common mistakes
- Treating one formula as a personal prescription.
- Ignoring frame size at the edges of height.
- Converting height wrong: 5 ft 9 in is 69 inches, not 59.
- Chasing the line while losing muscle on crash diets.
- Applying adult lines to children.
Try it yourself
Quick checks. Answers sit tucked under each question.
Robinson for a woman at 165 cm (64.96 in)?
4.96 in over five feet. 49 + 1.7 x 4.96 = 57.4 kg.
Devine for the same woman?
45.5 + 2.3 x 4.96 = 56.9 kg.
Questions
Robinson or Devine: which is right?
Both estimate. Robinson fits general builds, Devine runs heavier from drug dosing roots. Aim between them.
What if I am large framed?
Add roughly ten percent to the span. Wrist size hints at frame: over 7.5 in at the wrist reads large for men.
Do athletes use these?
Loosely. Muscle outweighs the lines, so body fat and performance matter more.
What about Hamwi and Miller?
Sibling formulas with nearby answers. Hamwi: men 48 + 2.7 per inch over five feet in kg.
How often should I weigh?
Weekly under fixed conditions tracks trends without daily noise.
Is BMI better?
Different lens. Pair ideal weight with BMI 18.5 to 24.9 and waist under half height.