Ideal Weight Calculator — the Range, Not a Number

There is no ideal weight. There is a healthy weight range, and it is wide: at 5 ft 7 in it runs from 119 to 159 lb. No US health agency publishes a single target number — the NHLBI and the NIDDK both define healthy weight as a BMI band of 18.5 to 24.9, and everything below is the band converted into pounds for your height.

The height field takes centimeters; feet and inches to meters converts yours if you need it.

The band in pounds, for common heights

Height	Healthy weight	Width of the band
5 ft 0 in	95–128 lb	33 lb
5 ft 2 in	102–136 lb	34 lb
5 ft 4 in	108–145 lb	37 lb
5 ft 6 in	115–154 lb	39 lb
5 ft 8 in	122–164 lb	42 lb
5 ft 10 in	129–174 lb	45 lb
6 ft 0 in	137–184 lb	47 lb
6 ft 2 in	145–194 lb	49 lb

Each row is the BMI formula run backwards: weight = BMI × height (in)² ÷ 703, at the 18.5 and 24.9 cutoffs. The full BMI chart carries every height between 4 ft 10 in and 6 ft 6 in.

Where “ideal body weight” actually came from

This is the part the phrase hides. The equation most calculators are running is Devine, 1974, and it was not written to describe a healthy body. It appeared in a note about dosing the antibiotic gentamicin, because some drugs distribute through lean tissue and dosing them by actual weight overshoots in a heavier patient.

Pai and Paloucek traced the lineage in 2000 and found no clinical study underneath it: the equation restated an old rule of thumb pulled from insurance height–weight tables. Robinson’s 1983 paper, which produced the second-most-used equation, is titled Determination of ideal body weight for drug dosage calculations — the purpose is in the title.

That history is still live. Ventilator tidal volume in US intensive care is set at 6 mL per kilogram of predicted body weight, and predicted body weight is Devine’s equation, unchanged. It is a dosing input, and it is very good at that job. It was never a health target.

A newer equation that returns a range instead of a point

Peterson and colleagues published a replacement in the American Journal of Clinical Nutrition in 2016, and its design says everything: instead of one ideal number, it computes body weight at any target BMI, so the output is a range you choose.

In US units it is weight (lb) = 5 × BMI + (BMI ÷ 5) × (height − 60 in). At 5 ft 7 in and a target BMI of 22: 5 × 22 + 4.4 × 7 = 141 lb. The authors state plainly that no single ideal weight applies across all conditions, and their reported error against national survey data is about a pound.

What the band cannot see

Two numbers go in, so only two numbers come out. The band does not know whether your weight is muscle or fat, and it does not know where the fat sits — abdominal fat carries the risk, which is why the NHLBI pairs the range with a waist threshold of 35 inches for women and 40 inches for men. It is also the wrong tool during pregnancy and under age 20.

If you want the reading from the other direction — your current weight scored against the same cutoffs — use the BMI calculator, or read what BMI actually measures first. To see how far the old formulas drift from the band, compare ideal weight and BMI side by side.

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