Broca Index Calculator
The Broca index gives a quick estimate of your ideal body weight from height alone, then compares your actual weight to it as a percentage. Enter your gender, height, and weight to see your Broca ideal weight and where you sit relative to it.
- Simple historical formula; less accurate than BMI or body fat methods.
Formula
Ideal weight = (height − 100) × 0.9 (men) or × 0.85 (women); Broca index = weight / ideal × 100
- Broca's rule estimates ideal weight as height in centimetres minus 100, adjusted by gender.
- For men the result is multiplied by 0.9 and for women by 0.85 to reflect typical body composition differences.
- The Broca index then expresses your actual weight as a percentage of that ideal: 100% means you're right on it.
- Values around 90–110% are usually considered near ideal; above ~120% suggests overweight by this measure.
- It's a simple historical rule — BMI or body-fat methods give a more reliable picture for most people.
Man, 175 cm, 75 kg
Inputs
- Height: 175 cm
- Current Weight: 75 kg
Ideal weight = (175 − 100) × 0.9 = 67.5 kg. Broca index = 75 ÷ 67.5 × 100 ≈ 111%, slightly above ideal.
Frequently asked questions
What is the Broca index?
It's a classic formula that estimates ideal body weight from height and compares your actual weight to it as a percentage.
How accurate is the Broca formula?
It's a rough rule of thumb. It ignores frame size and body composition, so BMI or body-fat measurements are generally more reliable.
What Broca index is healthy?
Around 90–110% is typically viewed as near ideal. Higher values suggest excess weight and lower values suggest being underweight by this measure.
Why does gender change the result?
The formula applies a higher multiplier for men (0.9) than women (0.85) to account for differences in average muscle mass and build.
Should I rely on this for health decisions?
No. Use it as a quick reference only and consult a healthcare professional for proper assessment of healthy weight.
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