How to use the ideal weight calculator
Choose your units, select your sex and enter your height. The calculator shows the result of four published ideal body weight (IBW) formulas, the range they span, their average, and the weight range that corresponds to a healthy BMI of 18.5 to 24.9 at your height.
The four formulas
Each formula starts from a base weight at 5 feet (60 inches) and adds a fixed amount for every inch above that:
| Formula | Men | Women |
|---|---|---|
| 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 |
| Devine (1974) | 50 kg + 2.3 kg per inch | 45.5 kg + 2.3 kg per inch |
| Hamwi (1964) | 106 lb + 6 lb per inch | 100 lb + 5 lb per inch |
Hamwi is the oldest, published by G. J. Hamwi in 1964 as a quick rule of thumb for diet planning. Devine appeared in 1974 in a paper on dosing the antibiotic gentamicin, and it is still widely used in medicine to calculate drug doses. Robinson and Miller both published revised versions in 1983. Hamwi's formula is applied here in its original pounds; the others in their original kilograms.
Worked example
For a woman who is 5 ft 4 in tall (4 inches over 5 feet):
- Robinson: 49 + 1.7 × 4 = 55.8 kg ≈ 123.0 lb
- Miller: 53.1 + 1.36 × 4 = 58.54 kg ≈ 129.1 lb
- Devine: 45.5 + 2.3 × 4 = 54.7 kg ≈ 120.6 lb
- Hamwi: 100 + 5 × 4 = 120 lb
The formulas span about 120 to 129 lb. Her healthy BMI range at the same height is much wider — about 107.8 to 145.1 lb — because BMI describes a range of healthy weights rather than a single target.
Why the formulas disagree
Each formula was fitted to different data for a different purpose, and none of them looks at body composition. They give a single number for everyone of the same height and sex, regardless of muscle mass, bone structure, age or ethnicity. Hamwi suggested adjusting his result by about 10% down for a small frame or 10% up for a large frame, which shows how wide a reasonable target really is. Treat the spread between the formulas as a rough zone, not a precise goal.
Heights under 5 feet
All four formulas were designed for heights of 5 feet and above. Some references extend them downward by subtracting the same per-inch amount for each inch under 5 feet, and clinicians sometimes use other adjustments. At shorter heights a straight subtraction quickly produces weights that fall below a healthy BMI, so for heights under 5 feet this calculator shows only the BMI-based healthy range. Your doctor or dietitian can advise on a suitable target.
Ideal weight versus a healthy weight range
"Ideal body weight" is mainly a clinical reference number — for example, for some drug doses and for setting ventilator volumes. For everyday health, a range is more useful than a single figure. The BMI calculator explains the healthy range, and a body fat estimate tells you more about how much of your weight is muscle.
When to see a professional
If you are planning to lose or gain a significant amount of weight, or you have a medical condition, speak with your doctor or a registered dietitian. They can set a target that reflects your health, body composition and history rather than height alone.
Important: results are estimates for general information only and are not medical advice. They cannot replace an assessment by a doctor, registered dietitian or other qualified health professional.
Frequently asked questions
Which ideal weight formula is the most accurate?
None is “correct” for everyone. They were fitted to different data, and none considers muscle or frame size. Many clinicians use Devine for drug dosing; for personal goals, the spread across all four plus the healthy BMI range is more helpful than any single number.
Why is my ideal weight different from the healthy BMI range?
The formulas give one number for your height, while BMI defines a range of weights associated with lower health risk. The formula results usually sit inside the BMI range, toward the middle or lower half.
Does ideal weight take muscle into account?
No. Muscular people often weigh more than their “ideal” weight while having little body fat. A body fat estimate is a better guide in that case.
How does frame size affect ideal weight?
Hamwi suggested subtracting about 10% for a small frame and adding about 10% for a large frame. Frame size is often judged from wrist circumference or elbow breadth.
Why are heights under 5 feet handled differently?
The formulas were built for heights of 5 feet and above. Extending them downward can give weights below a healthy BMI, so the calculator shows only the BMI-based healthy range for shorter adults.
Last updated: October 8, 2026