Ideal Weight Calculator

Ideal Body Weight (IBW) formulas were developed in clinical settings to dose medication and plan nutrition — not to set aesthetic goals. Hamwi (1964) was originally a quick bedside heuristic for insulin dosing in diabetic patients; Devine (1974) refined it for aminoglycoside antibiotic dosing in renal-impaired adults; Robinson (1983) and Miller (1983) re-derived the curves against larger population samples.

All four formulas share the same shape: a baseline weight at 5 ft (60 in / 152 cm) plus a per-inch increment above that. They differ in baseline and slope — Hamwi is the most generous (heaviest predictions), Miller is the most conservative.

Real-world body composition matters more than IBW. A muscular athlete will read 'overweight' on these formulas because they assume average lean mass; a sedentary adult at 'ideal' weight may still have unhealthy body fat. Use the BMI healthy-weight range alongside IBW for a fuller picture.

Frame size accounts for skeletal differences. The standard Hamwi adjustment is ±10%: small frame = baseline × 0.9, large frame = baseline × 1.1. Medium frame = baseline.

Quick frame test (wrist circumference, MetLife method): for a male over 5'5", small < 6.25", medium 6.25–6.75", large > 6.75". For a female 5'2"–5'5", small < 6", medium 6–6.25", large > 6.25". Or use the elbow-breadth method documented in Frisancho (1984).

Frame size has no effect on body fat percentage targets — it only adjusts where 'normal' lean mass sits on a height-vs-weight curve.

A 5'10" (70 in) male with a medium frame: Hamwi = 48 + 2.7 × 10 = 75.0 kg (165 lb). Devine = 50 + 2.3 × 10 = 73.0 kg (161 lb). Robinson = 52 + 1.9 × 10 = 71.0 kg (157 lb). Miller = 56.2 + 1.41 × 10 = 70.3 kg (155 lb).

Four-formula average ≈ 72 kg (160 lb). Healthy-BMI range at the same height is 58–78 kg (129–172 lb), so the IBW estimate sits comfortably inside the healthy band.

The same 5'10" male with a large frame would target ~79 kg (174 lb) under Hamwi+10% — at the top of the healthy-BMI range, consistent with a heavier-boned but lean physique.

Don't treat IBW as a goal weight if you're already in the healthy-BMI range with normal body fat — chasing a number below your set point usually backfires.

These formulas understate ideal weight for athletes carrying significant muscle mass. A 6-foot rugby prop at 105 kg can be lean and healthy despite reading 35 kg above Robinson IBW.

Pediatric and adolescent patients need different references — IBW formulas above are for adults 18+.

If you're being prescribed weight-based medication, your clinician will pick one specific formula (often Devine for antibiotics, Hamwi for older protocols). Don't substitute the average.

Reassess frame size honestly. Most people guess 'large' when they're actually medium — wrist or elbow breadth is the only reliable measure.