Ideal Weight Calculator
Enter your height and sex to see your ideal weight range from the Devine, Hamwi and BMI formulas.
This tool is for information only and does not replace a doctor or dietitian. Talk to one before making health decisions.
How Is Ideal Weight Determined?
Ideal weight is a range, not a single number. The Devine, Hamwi and BMI formulas each work out a healthy weight for your height in a different way. This tool shows all three side by side, so you see a realistic target range instead of one figure.
What Is Ideal Weight and Why Is It Not a Single Number?
In medicine, 'ideal weight' is the weight range thought to keep health risks lowest for a given height. The formulas come from different places: Devine and Hamwi were first developed to work out clinical drug doses, while the BMI range spread through public health use.
For a 180 cm man, for example, Devine gives 75.0 kg, Hamwi gives 77.3 kg and the BMI range is 59.9–80.7 kg. The spread shows that each formula is only an estimate.
The Effect of Age on Ideal Weight
The Devine and Hamwi formulas do not account for age. Yet muscle mass falls and the share of fat changes as you get older, so it makes more sense to read the results with a doctor or dietitian later in life.
Formulas and Logic
The tool first converts your height from centimetres to inches, then calculates the excess over 60 inches (5 feet ≈ 152 cm). Devine (male): 50 + 2.3 × (inches over); for females the base is 45.5. Hamwi (male): 48 + 2.7 × (inches over); for females the base is 45.5 and the multiplier is 2.2. The BMI range is obtained by multiplying the 18.5 and 24.9 thresholds by the square of the height in metres.
Example Scenarios
| Profile | Devine | Hamwi | BMI Range |
|---|---|---|---|
| Male · 170 cm | 65.9 kg | 66.7 kg | 53.5–71.9 kg |
| Male · 180 cm | 75.0 kg | 77.3 kg | 59.9–80.7 kg |
| Female · 160 cm | 52.4 kg | 52.1 kg | 47.4–63.7 kg |
| Female · 165 cm | 56.9 kg | 56.4 kg | 50.4–67.8 kg |
What Should You Do If You're Not at Your Ideal Weight?
The three values complement each other. Devine and Hamwi each give a single value, while the BMI range shows a wider safe zone. In practice, aiming to stay between the lower and upper limits of the BMI range is the broadest approach.
If your weight is well above this range, small steps are the sustainable way forward. If you are below it, remember that being underweight carries its own health risks. Either way, a dietitian or doctor can guide you.