Broca Index Calculator
The 19th-century Broca reference (height in cm − 100) and its modified form — where 'ideal weight' formulas began.
Paul Broca's 1871 rule of thumb predates BMI by a century and survives in everyday speech ('height minus 100'). It overestimates at tall heights and underestimates at short ones, which is exactly why later formulas added slopes — shown here for historical and comparative interest.
Formula
For general information only — not medical advice, a diagnosis or a treatment plan. Consult a qualified healthcare professional before making health, diet, medication or exercise decisions.
The 19th-century Broca reference (height in cm − 100) and its modified form — where 'ideal weight' formulas began. The Broca Index Calculator is a free, private broca index tool — every result computes instantly in your browser with no sign-up and no data upload.
About Broca Index Calculator
Paul Broca's 1871 rule of thumb predates BMI by a century and survives in everyday speech ('height minus 100'). It applies Broca = height(cm) − 100; modified = Broca × 0.90 (M) / 0.85 (F). Use the Broca Index Calculator to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Broca Index Calculator
- 1Enter your details in the Broca Index Calculator input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Broca Index Calculator?
- ✓Instant broca index result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Broca P (1871), Mémoires d'anthropologie)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Broca Index Calculator work?+
Paul Broca's 1871 rule of thumb predates BMI by a century and survives in everyday speech ('height minus 100'). The calculation uses the formula: Broca = height(cm) − 100; modified = Broca × 0.90 (M) / 0.85 (F). Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Broca Index Calculator accurate, and what is it based on?+
The method is traceable to authoritative sources, including Broca P (1871), Mémoires d'anthropologie; Weber-Sanchez A, Int J Fam Commun Med 2023 — Broca vs BMI review. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Broca Index Calculator free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is for general information only and is not medical advice. Always consult a qualified healthcare professional before making health decisions.
What can I use the Broca Index Calculator for?+
It's commonly used for broca index, broca formula, height minus 100. The 19th-century Broca reference (height in cm − 100) and its modified form — where 'ideal weight' formulas began.
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