Ideal & Healthy Weight Calculator

Ideal body weight (IBW) is an estimate of the healthiest weight range for a person of a given height and sex. It is typically calculated with formulas like the Hamwi (1964) or Devine (1974) equations, which use a 5-foot baseline plus a per-inch increment, or from the WHO healthy BMI band of 18.5–24.9 scaled to your height. Our calculator shows all three methods side by side so you can see how they compare.

The Hamwi formula (1964) uses 48 kg + 2.7 kg per inch over 5 feet for men, and 45.4 kg + 2.2 kg for women. The Devine formula (1974) uses 50 kg + 2.3 kg per inch for men and 45.5 kg + 2.3 kg for women. Devine is now the clinical standard — it is the equation used to calculate medication dosages and mechanical ventilation settings in hospitals. The two formulas usually agree within a few kilograms.

For clinical purposes, the Devine formula is the most widely used and validated, particularly for drug dosing. However, all IBW formulas are statistical estimates based on average body frames — they do not account for muscle mass, bone density, or individual body composition. The WHO BMI-based healthy weight range (18.5–24.9) is generally considered the most useful for general health guidance, since it presents a range rather than a single target.

A healthy weight range is computed from the WHO BMI classification: for any height, the healthy range is roughly BMI 18.5 to 24.9. In metric terms, that is weight = BMI × height(m)². For example, a 170 cm person has a healthy range of about 53.5–72.0 kg. Our calculator displays this range automatically along with the midpoint and the classic formula estimates.

No. Because men generally have higher muscle mass and bone density than women, IBW formulas apply different constants for each sex. Hamwi starts men at 48 kg and women at 45.4 kg for 5 feet; Devine starts men at 50 kg and women at 45.5 kg. Both formulas also apply the same per-inch increment (2.2–2.7 kg depending on formula), so the gap between sexes stays roughly constant across heights.

Yes. IBW formulas assume an average body composition, so a muscular athlete may be "over" the formula estimate while carrying a healthy amount of body fat. Conversely, someone at their formula weight could still have low muscle mass and high body fat. For this reason, body composition metrics — like the body fat percentage and lean mass breakdown — are often more informative than a single ideal weight number.

The Devine formula is the standard used in clinical settings to calculate ideal body weight for medication dosing, nutrition support, and ventilator tidal volume. Dosing on actual body weight can overdose heavier patients, while dosing on IBW ensures safe, consistent levels. Our free calculator gives you the same Devine estimate used clinically — no registration required.

Yes. The calculator is 100% free with no registration, and every calculation runs entirely in your browser — no data is ever sent to a server. If you choose to save results, they are stored only in your browser's localStorage, and you can export, import, or clear your history at any time.