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⚖️ BMI Calculator

Calculate your Body Mass Index (BMI) using metric or imperial units.

Your BMI
Underweight
< 18.5
Normal
18.5–24.9
Overweight
25–29.9
Obese
≥ 30

What is a BMI Calculator?

BMI stands for Body Mass Index — a simple numerical value calculated from a person's weight and height. It provides a reliable indicator of body fatness for most people and is used worldwide by doctors, nutritionists, and health organisations to screen for weight categories that may lead to health problems. BMI is defined as weight in kilograms divided by height in metres squared (kg/m²).

The World Health Organisation (WHO) defines four categories: Underweight (BMI below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). While BMI is a useful screening tool, it does not directly measure body fat or account for muscle mass, bone density, age, or ethnicity — always consult a healthcare professional for a full health assessment.

How to Use the BMI Calculator

  1. Choose your unit system: Metric (kg and cm) or Imperial (lb, ft, and inches).
  2. 输入您的 weight and height in the appropriate fields.
  3. 点击 Calculate BMI.
  4. Your BMI value and category (Underweight / Normal / Overweight / Obese) will appear with colour coding.

Why Use Our BMI Calculator?

  • 100% 免费 — No cost, no ads injected into results.
  • 无需注册 — Start calculating immediately without an account.
  • 基于浏览器 — Your health data is processed locally and never transmitted.
  • Metric & Imperial — Switch between kg/cm and lb/ft/in with one click.
  • WHO Categories — Results are colour-coded using the official WHO BMI classification.

常见问题解答

According to the WHO, a BMI of 18.5 to 24.9 is considered normal weight for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese. These ranges apply to adults aged 18 and over regardless of sex.

BMI can overestimate body fat in athletes and muscular individuals because muscle weighs more than fat. A bodybuilder may have a BMI in the "overweight" range while having very low body fat. Conversely, some people with a normal BMI may carry excess visceral fat. BMI is a population-level screening tool, not a diagnostic measure.

BMI = weight (kg) ÷ height² (m²). For imperial units, the formula is: BMI = (weight in pounds × 703) ÷ height in inches². For example, a person weighing 70 kg at 175 cm tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9.

No. For children and teenagers (ages 2–19), BMI is assessed against age- and sex-specific growth charts (BMI-for-age percentiles). The same number means different things at different ages. Paediatric BMI assessment should always be done by a healthcare provider.

要闻速览

  • ✓ 100% 免费，无隐藏费用
  • ✓ 无需帐户或登录
  • ✓ 适用于任何浏览器
  • ✓ 您的数据永远不会离开您的设备
  • ✓ Supports both metric and imperial units

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