Complete guide
Reviewed July 2026'How much should I weigh?' has no single perfect answer - but several well-established formulas give a sensible target range for a given height and sex. Ideal Body Weight (IBW) estimates originated in medicine, where they're used to dose drugs and set clinical goals, and they remain a useful reality check for personal health.
This calculator estimates your ideal weight from height and sex. Below you'll find the main formulas (Devine, Robinson, Hamwi and the BMI-range method), worked examples, and - just as important - an honest account of what these estimates can and cannot tell you, since muscle, frame size and body composition all move the real answer.
Treat IBW as a guide, not a verdict. A healthy weight is a range, not a single number, and how that weight is composed matters more than the number on the scale.
Ideal weight formulas
Devine (1974), for height above 5 ft (60 in): Men: IBW = 50 kg + 2.3 kg x (inches over 5 ft) Women: IBW = 45.5 kg + 2.3 kg x (inches over 5 ft)
The Devine formula is the most widely used, originally created for medication dosing. It starts from a base weight at 5 feet and adds a fixed amount per inch of extra height. Robinson and Hamwi are close variants with slightly different constants; all give similar answers within a few kilograms.
The BMI-range method
A modern, arguably better approach is to work backwards from a healthy BMI band (18.5-24.9): ideal weight range = 18.5 x height(m)^2 to 24.9 x height(m)^2. This gives a range rather than a single number, which better reflects that health tolerates variation. For Asian populations, a lower band (18.5-22.9) is often used.
Worked examples
- Man, 178 cm (70 in, 10 inches over 5 ft): Devine IBW = 50 + 2.3 x 10 = 73 kg.
- Woman, 165 cm (65 in, 5 inches over 5 ft): Devine IBW = 45.5 + 2.3 x 5 = 57 kg.
- BMI-range for 178 cm (1.78 m): 18.5 x 1.78^2 to 24.9 x 1.78^2 = 58.6 to 78.9 kg - a healthy range, with 73 kg comfortably inside.
- BMI-range for 165 cm (1.65 m): 50.4 to 67.8 kg - the 57 kg Devine figure sits in the lower-middle.
What ideal weight can and cannot tell you
Strengths and limits
- Useful as a quick target range and for clinical dosing where a standardized figure is needed.
- Blind to muscle vs fat: a lean, muscular person may exceed their IBW while being very healthy.
- Ignores frame size: large-framed people naturally carry more healthy weight than small-framed people of the same height.
- Sex-specific but not ethnicity-adjusted in the classic formulas; Asian populations often use lower targets.
- A range (BMI method) is more honest than a single number (Devine) - real health spans several kilograms.
Frame size adjustment
A rough frame check: wrap your thumb and middle finger around the opposite wrist. If they overlap, you're likely small-framed (aim lower in the range); if they just touch, medium; if they don't meet, large-framed (aim higher). Clinicians estimate frame more precisely from wrist circumference or elbow breadth, but the finger test is a handy field version.
Using this calculator
- Enter your height and sex to get the estimated ideal weight.
- Treat the number as the centre of a range - a few kilograms either way is normal and healthy.
- Cross-check with the BMI healthy-weight range for your height for a fuller picture.
- Adjust up for a large frame or high muscle mass, and down for a small frame.
Common mistakes
- Treating IBW as an exact goal rather than the middle of a healthy range.
- Ignoring muscle mass - athletes routinely and healthily exceed their IBW.
- Overlooking frame size, which shifts a healthy weight by several kilograms.
- Using men's constants for women or vice versa.
- Fixating on the scale while ignoring waist size and body composition, which matter more for health.
Frequently asked questions
Glossary
- Ideal Body Weight (IBW)
- An estimated healthy weight for a given height and sex.
- Devine formula
- The most common IBW formula, base weight plus 2.3 kg per inch over 5 feet.
- BMI-range method
- Deriving a healthy weight range from the 18.5-24.9 BMI band.
- Frame size
- Skeletal build (small/medium/large) that shifts healthy weight.
- Body composition
- The proportion of muscle, fat and bone - more telling than weight alone.
- Lean body weight
- Weight excluding fat; used for some drug dosing.
- Robinson/Hamwi
- Close variants of the Devine IBW formula with different constants.
- Healthy weight range
- The span of weights consistent with good health for a height, not a single number.
Key takeaways
Ideal weight is a range, not a single number. The Devine formula (base weight + 2.3 kg per inch over 5 feet) gives a standard clinical figure, while the BMI-range method (18.5-24.9 x height in m squared) gives a healthier range. Both ignore muscle and frame size, which move the real answer by several kilograms - so treat IBW as a guide, aim within the range, and weigh body composition and waist size more heavily than the scale.
Enter your height and sex above for your ideal-weight estimate; then check it against the BMI healthy-weight range and adjust for your frame and muscle.