Devine Formula — Ideal Body Weight for Dosing

The Devine formula, published in 1974, returns one ideal body weight in kilograms from height and sex: 50 kg for a man at five feet, 45.5 kg for a woman, plus 2.3 kg for every inch above that. It was written to calculate drug doses, and half a century later that is still its main job in American hospitals.

The field takes centimeters, where the same slope is about 0.9 kg per cm above 152.4 cm.

The equation, worked in inches

A man of 5 ft 10 in is 70 inches, ten above the baseline:

IBW = 50 + 2.3 × 10 = 73.0 kg = 161 lb

A woman of 5 ft 4 in is 64 inches, four above:

IBW = 45.5 + 2.3 × 4 = 54.7 kg = 121 lb

Height	Men	Women
5 ft 0 in	110 lb (50.0 kg)	100 lb (45.5 kg)
5 ft 2 in	120 lb (54.6 kg)	110 lb (50.1 kg)
5 ft 4 in	131 lb (59.2 kg)	121 lb (54.7 kg)
5 ft 6 in	141 lb (63.8 kg)	131 lb (59.3 kg)
5 ft 8 in	151 lb (68.4 kg)	141 lb (63.9 kg)
5 ft 10 in	161 lb (73.0 kg)	151 lb (68.5 kg)
6 ft 0 in	171 lb (77.6 kg)	161 lb (73.1 kg)

Two things fall out of the table. Each inch is worth about 5.1 lb, always — the line never bends. And the women’s column is the men’s column minus 10 lb at every single height, because the sex term is a constant, not a slope.

It was written to dose an antibiotic

Ben Devine’s equation appeared in a 1974 note about gentamicin, an aminoglycoside antibiotic that distributes through lean tissue rather than fat. Dosing it by actual body weight overshoots badly in a heavier patient, so clinicians needed a stand-in weight that tracked frame rather than adiposity.

Pai and Paloucek went looking for the evidence base in 2000 and did not find one. The equation restated a rule of thumb drawn from insurance height–weight tables, and the later equations that tried to improve on it — by regression on the same tables — came out looking almost identical. That shared ancestry is why Robinson’s version sits within a few pounds of Devine’s at most heights.

Where it is still used every single day

Open a US intensive care unit and Devine’s numbers are on the ventilator. Lung-protective ventilation sets tidal volume at 6 mL per kilogram of predicted body weight, and predicted body weight is Devine’s equation with the sexes unchanged. For the 5 ft 10 in man above, 73.0 kg means a target tidal volume near 438 mL.

That use case explains a detail that looks strange on a consumer page: predicted body weight is deliberately independent of what the patient actually weighs, because lungs do not grow with body fat. It also means an error in the height measurement is multiplied straight into the ventilator setting — one PMC analysis calculated a factor of 5.5 between height error and tidal volume error.

What it is not

It is not a health target, and nothing about it was ever validated as one. It has no term for your current weight, your age, your muscle mass or your waist. Two people the same height and sex get the same answer whether one runs marathons and the other has not stood up in a week.

The NHLBI and the NIDDK do not publish an ideal weight at all — they publish a healthy range, BMI 18.5 to 24.9, which at 5 ft 10 in runs 129 to 174 lb. Devine’s 161 lb sits inside that band but well above its middle. If you came here for a weight goal rather than a dose, the ideal weight calculator gives the band, and the BMI chart gives it for every height.

This content is informational and does not replace evaluation by a health professional.