---
title: "How to Calculate BMI — WHO Formula, Country Thresholds Explained"
description: "Learn the BMI formula step by step. Metric and imperial versions. See how BMI classifications differ between WHO, Japan (JASSO), Asia-Pacific, and China standards — and why."
url: "https://worldcalculators.org/learning/how-to/bmi/"
canonical: "https://worldcalculators.org/learning/how-to/bmi/"
---

# How to Calculate BMI

Learn the BMI formula step by step. Metric and imperial versions. See how BMI classifications differ between WHO, Japan (JASSO), Asia-Pacific, and China standards — and why.

## Quick answer

BMI = weight(kg) ÷ height(m)² . Example: 70 kg at 1.75 m → 70 ÷ 3.0625 = BMI 22.9. That's "Normal" by WHO — but the same BMI could be classified differently in Japan or by Asia-Pacific guidelines. The formula is universal; the category thresholds are not.

## The BMI Formula

Imperial: BMI = 703 × weight (lb) ÷ height (in)²
Divide centimetres by 100. 175 cm = 1.75 m. Then square it: 1.75 × 1.75 = 3.0625 m².

## BMI Classification Thresholds by Standard

Key insight: A BMI of 26 is "Overweight" by WHO but "Obese Grade I" by Japan's JASSO standard. The same number, different meaning.

Source: https://worldcalculators.org/learning/how-to/bmi/
Markdown mirror of the HTML page. Prefer this URL for RAG; the interactive calculator still lives on the HTML page.