Broca Index Ideal Weight
A nineteenth-century calculation still printed on hospital forms. Multiply by 0.9 for men and 0.85 for women. Its virtue is that you can do it in your head; it lands a little below BMI-based figures.
Your numbers
Broca weight
64.8kg
Percentage
114.2%
Difference
9.2kg
Formula
Broca weight = (Height (cm) − 100) × (0.9 × Sex (M1 / F0) + 0.85 × (1 − Sex (M1 / F0)))
Accuracy falls away at the extremes. Below 150 cm or above 190 cm, use the BMI-based healthy range instead.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Height (cm) (cm)Height in centimetres; converted to metres inside the formula. | 172 | 100 and up |
| Sex (M1 / F0)Where the formula splits by sex — enter 1 for male, 0 for female. | 1 | 0 ~ 1 |
| Weight (kg) (kg)The second weight you are comparing against. | 74 | 1 and up |
Step by step
Quick reference table
Results when only Height (cm) (cm) changes and everything else stays put.
| Height (cm) (cm) | Broca weight (kg) | Percentage (%) | Difference (kg) |
|---|---|---|---|
| 100 | 0 | 0 | 74 |
| 129 | 26.1 | 283.5 | 47.9 |
| 172 | 64.8 | 114.2 | 9.2 |
| 258 | 142.2 | 52 | -68.2 |
| 344 | 219.6 | 33.7 | -145.6 |
What each result means
| Result | At default values |
|---|---|
| Broca weight (kg)Height minus 100, times a factor — the classic reference weight. | 64.8 |
| Percentage (%)A share expressed out of 100. | 114.2 |
| Difference (kg)The gap between two values — a quantity, not a rate. | 9.2 |
Common mistakes
Accuracy falls away at the extremes. Below 150 cm or above 190 cm, use the BMI-based healthy range instead.
Glossary
- Height (cm)
- Height in centimetres; converted to metres inside the formula.
- Sex (M1 / F0)
- Where the formula splits by sex — enter 1 for male, 0 for female.
- Weight (kg)
- The second weight you are comparing against.
- Broca weight
- Height minus 100, times a factor — the classic reference weight.
- Percentage
- A share expressed out of 100.
- Difference
- The gap between two values — a quantity, not a rate.
Frequently asked questions
Q. How is Broca Index Ideal Weight calculated?
Broca weight = (Height (cm) − 100) × (0.9 × Sex (M1 / F0) + 0.85 × (1 − Sex (M1 / F0))) — A nineteenth-century calculation still printed on hospital forms. Multiply by 0.9 for men and 0.85 for women. Its virtue is that you can do it in your head; it lands a little below BMI-based figures.
Q. Can you walk through an example?
With Height (cm) 172cm, Sex (M1 / F0) 1, Weight (kg) 74kg, the answer is Broca weight 64.8kg.
Q. What do I need to enter?
Enter Height (cm), Sex (M1 / F0), Weight (kg). The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Height (cm) (cm) moves the answer to Height (cm) (cm) 100 → Broca weight (kg) 0 and Height (cm) (cm) 344 → Broca weight (kg) 219.6. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Accuracy falls away at the extremes. Below 150 cm or above 190 cm, use the BMI-based healthy range instead.
Related calculators
These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.