Ideal Weight Calculator

Where “ideal weight” formulas actually come from

None of the four formulas on this page was invented to tell you what to weigh. Hamwi (1964) was a quick bedside rule for clinical nutrition; Devine (1974) was created to dose medications whose safe amounts scale with lean body size, and it remains embedded in pharmacology today; Robinson and Miller (both 1983) were statistical refinements once better population data existed. They share one structure — a base weight at 5 feet, plus a fixed amount per inch above it — which is why they agree reasonably well at average heights and fan out at the extremes. Understanding that lineage is the key to using them: they are clinical reference points, not aesthetic targets, and the spread between them is honest uncertainty, not a bug.

Reading the spread: a worked example

For a woman of 5′6″, the four formulas land at roughly 129–135 lb (58.7–61.3 kg) — Hamwi lowest, Miller highest, Devine and Robinson nearly identical at 131 lb. The healthy-BMI range for the same height is far wider: about 115–154 lb (52–70 kg). That comparison is the single most useful thing on this page. The formulas cluster in the lower-middle of the evidence-based band, so someone at 150 lb and 5′6″ is 15–20 lb “above ideal” by formula yet comfortably inside the range population studies associate with good health. For a man of 5′10″ the same pattern holds: formulas from 155 to 165 lb, with Hamwi highest for men and Miller lowest — the ordering flips between sexes because each author fitted different per-inch increments.

What height alone cannot see

• Composition.A 5′10″ man at 180 lb could be 12% body fat or 28% — same formula verdict, opposite health picture. The body fat calculator distinguishes the two with a tape measure.
• Frame.Wrist and shoulder breadth vary enough that two healthy people of one height can differ by 10 kg of bone and muscle alone. Older clinical practice added ±10% for small or large frames — a crude but honest admission of the formulas’ limits.
• Age. Some muscle loss with age is normal, and modest extra weight in older adults is not associated with the same risks as in the young. The formulas apply one number to a 25-year-old and a 75-year-old.

Turning a zone into a plan

The practical reading order: start with the healthy-BMI range as the evidence-based zone (the BMI calculator shows where your current weight sits in it), use the formula cluster as a reference point within that zone, and let composition — not the scale — arbitrate the last few kilograms. If a change is warranted, the calorie calculator converts a target rate of loss or gain into a daily energy budget. A target zone of a few kilograms, approached at 0.25–0.45 kg a week, survives real life far better than a single magic number — and the difference between weighing 131 lb and 137 lb at 5′6″ is invisible to every health outcome that matters.