Ideal Body Weight Calculator

What “ideal body weight” really means

The term “ideal body weight” comes from clinical medicine, not from fitness or aesthetics. The four classical formulas — Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) — were created to give clinicians a single anchor weight, primarily so that drug doses for medications with narrow therapeutic windows could be standardized for patients of a given height.

They were never designed as personal health goals, and they do a poor job of one because they don’t see your lean mass, frame size, body composition, or fitness level. We show them anyway because they’re widely cited and because a side-by-side comparison reveals their disagreement — useful context for anyone who’s been told “you should weigh X.”

The four formulas

All four are linear functions of height above 5 feet (152 cm). All are reported in kilograms.

Devine (1974)

Men:   IBW = 50 kg + 2.3 × (height_in − 60)
Women: IBW = 45.5 kg + 2.3 × (height_in − 60)

The Devine formula was introduced for aminoglycoside antibiotic dosing. Despite its purely clinical origin, it became the most widely cited “ideal weight” formula in patient-facing tools.

Robinson (1983)

Men:   IBW = 52 kg + 1.9 × (height_in − 60)
Women: IBW = 49 kg + 1.7 × (height_in − 60)

Robinson’s formula generally produces slightly higher numbers than Devine for women and slightly different anchors for men.

Miller (1983)

Men:   IBW = 56.2 kg + 1.41 × (height_in − 60)
Women: IBW = 53.1 kg + 1.36 × (height_in − 60)

Miller’s formula is the most generous of the four — its lower per-inch coefficient produces lower numbers at tall heights but higher numbers at short heights.

Hamwi (1964)

Men:   IBW = 48 kg + 2.7 × (height_in − 60)
Women: IBW = 45.5 kg + 2.2 × (height_in − 60)

The oldest of the four. Heavily used in dietetic clinical practice through the 1970s–1990s. Aggressive on the per-inch slope, so produces the highest “ideal” numbers at tall heights.

BMI 18.5–24.9 healthy range

Lower bound: 18.5 × height(m)²
Upper bound: 24.9 × height(m)²

Not a single ideal — a band of healthy weights. For most lifters and recreational athletes, this is the more useful reference.

A worked example

A 180-cm man (180 cm = 70.87 in, so height_in − 60 = 10.87):

• Devine: 50 + 2.3 × 10.87 = 75.0 kg
• Robinson: 52 + 1.9 × 10.87 = 72.7 kg
• Miller: 56.2 + 1.41 × 10.87 = 71.5 kg
• Hamwi: 48 + 2.7 × 10.87 = 77.4 kg
• BMI healthy range (1.80 m): 59.9 kg – 80.6 kg

Spread across the four formulas: 5.9 kg, or about 8%. Notice that the BMI healthy range completely contains all four classical estimates — which is why we tend to recommend the BMI band as the more practical reference.

A 165-cm woman (165 cm = 64.96 in, so height_in − 60 = 4.96):

• Devine: 45.5 + 2.3 × 4.96 = 56.9 kg
• Robinson: 49 + 1.7 × 4.96 = 57.4 kg
• Miller: 53.1 + 1.36 × 4.96 = 59.8 kg
• Hamwi: 45.5 + 2.2 × 4.96 = 56.4 kg
• BMI healthy range (1.65 m): 50.4 kg – 67.8 kg

How to use this calculator

1. Enter height and sex.
2. Toggle metric or imperial.
3. Read all four formulas plus the BMI healthy range, side by side.
4. Don’t pick a single “ideal” — use the band as context.

What you should actually aim for

The pragmatic order of operations for setting body-weight targets:

1. Pick a body-fat percentage, not a weight. Most lifters do best in the 12–18% range (men) or 18–25% (women).
2. Hold lean mass with progressive resistance training.
3. Adjust calories until your weight settles inside the BMI healthy range (or slightly above, if you’re heavily muscled).
4. Re-check the body-fat number every 2–3 months.

This loop makes “ideal weight” a derived number — the weight you settle at when your body composition and training stimulus are dialed in — rather than a target imposed from above.

Where the formulas systematically fail

• Heavily muscled lifters. All four formulas underestimate ideal weight for trained athletes by 5–15 kg. Use waist-to-height ratio and body fat percentage instead.
• Very tall adults (> 200 cm) and very short adults (< 152 cm). The linear extrapolation breaks down. Hamwi is especially generous for tall adults; Miller is most conservative.
• Older adults. Lean-mass loss with age means the “ideal” weight that’s healthiest for a 30-year-old may not be ideal for the same person at 70.
• Pregnant women. Don’t use any of these.

Why we still show ideal-weight formulas

Despite their limitations, the formulas have practical uses:

• Medical contexts. Many drug doses are calculated against IBW. Knowing roughly where you sit relative to Devine or Robinson can help you anticipate clinical conversations.
• Setting an order-of-magnitude reference. If you’re 50% above your Devine number, you’re definitively in obese territory by every metric. If you’re at it, you’re roughly average. If you’re 20% below it, you’re underweight regardless of formula choice.
• Sanity-checking aspirational goals. A goal of 60 kg for a 180 cm man is below every classical formula and far below the BMI healthy range — that’s a useful flag.

The formulas are old, blunt instruments — useful for what they were designed to do (clinical dosing), poor for what they’re often misused for (personal physique targets).