What Is Ideal Body Weight?
Ideal Body Weight (IBW) is an estimated target weight range considered healthy for a given height and gender. No single number applies to everyone — bone density, muscle mass, and body frame all influence what “healthy” looks like. Using multiple formulas and averaging results gives a more realistic target range.
Formula 1: Broca’s Formula
Developed by French surgeon Paul Broca in the 19th century. Simple and widely cited.
Male: (Height in cm − 100) × 0.9
Female: (Height in cm − 100) × 0.85
Example — Male, 175cm: (175 − 100) × 0.9 = 67.5 kg
Strengths: Easy to calculate mentally
Weaknesses: Tends to underestimate for shorter people, overestimate for taller people
Formula 2: Lorentz Formula
Refines the Broca formula with a correction factor based on height deviation from 150cm.
Male: Height − 100 − (Height − 150) / 4
Female: Height − 100 − (Height − 150) / 2
Example — Male, 175cm: 175 − 100 − (175 − 150) / 4 = 68.75 kg
Strengths: More accurate for average heights (155–175cm)
Weaknesses: Less reliable at height extremes
Formula 3: BMI-22 Standard Weight
The most clinically referenced modern formula, targeting BMI 22 — the midpoint of the Asian normal range (18.5–22.9).
Ideal Weight (kg) = 22 × Height (m)²
Example — 175cm: 22 × (1.75)² = 67.4 kg
Strengths: Directly tied to evidence-based BMI research, most used in clinical settings
Weaknesses: Does not account for muscle mass or body frame
Which Formula Should You Use?
The average of all three formulas provides the best single target. For a male at 175cm:
| Formula | Result |
|---|---|
| Broca | 67.5 kg |
| Lorentz | 68.75 kg |
| BMI-22 | 67.4 kg |
| Average | 67.9 kg |
Use this average as your target, but allow a ±5 kg range depending on your body type and composition.
Beyond the Numbers
If you’re heavily muscular (athlete, weightlifter), the BMI-based formula will understate a healthy weight for you. Similarly, if you have a naturally fine bone structure, even the lower end of these formulas may feel slightly high. Use the calculator as a guide, not a prescription.