BMI Calculator

Calculate Body Mass Index (BMI) with metric or imperial units and see standard category ranges. For adults only; not a substitute for professional advice.

BMI
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Informational only; verify critical results independently.

How to use

  1. Choose metric (kg, cm) or imperial (lb, ft/in) using the unit toggle.
  2. Enter your weight in the weight field. Use a decimal if needed (e.g. 70.5 kg).
  3. Enter your height: in metric, use centimetres; in imperial, use feet and inches.
  4. The calculator updates as you type. Your BMI and category appear below the inputs.
  5. BMI categories shown are: Underweight (under 18.5), Normal (18.5–24.9), Overweight (25–29.9), Obesity (30+).
  6. These ranges are for adults. They are not valid for children, athletes with high muscle mass, or pregnant people.
  7. Use the result as a rough screening only. For health decisions, see a doctor or dietitian.

Examples

  • Metric: 70 kg, 175 cm
    Input: Weight 70 kg, Height 175 cm
    Output: BMI 22.9 (Normal weight)
  • Imperial: 154 lb, 5 ft 10 in
    Input: Weight 154 lb, Height 5 ft 10 in
    Output: BMI 22.1 (Normal weight)
  • Metric: 90 kg, 180 cm
    Input: Weight 90 kg, Height 180 cm
    Output: BMI 27.8 (Overweight)
  • Imperial: 200 lb, 6 ft 0 in
    Input: Weight 200 lb, Height 6 ft 0 in
    Output: BMI 27.1 (Overweight)
  • Metric: 55 kg, 170 cm
    Input: Weight 55 kg, Height 170 cm
    Output: BMI 19.0 (Normal weight)
  • Metric: 100 kg, 175 cm
    Input: Weight 100 kg, Height 175 cm
    Output: BMI 32.7 (Obesity)
  • Imperial: 130 lb, 5 ft 6 in
    Input: Weight 130 lb, Height 5 ft 6 in
    Output: BMI 21.0 (Normal weight)

FAQ

What is BMI?
Body Mass Index is weight in kilograms divided by height in metres squared (kg/m²). It’s a simple screening tool, not a measure of body fat or health on its own.
Why do metric and imperial give the same result?
The formula is the same; we convert imperial inputs to kg and metres before calculating. Small differences can appear due to rounding.
Is BMI accurate for everyone?
No. It doesn’t distinguish muscle from fat, so very muscular people can be classed as overweight. It also doesn’t apply to children, and should be used only as a rough guide for adults.
What are the standard BMI categories?
Underweight: under 18.5. Normal: 18.5–24.9. Overweight: 25–29.9. Obesity: 30 and above. These are WHO-style ranges for adults.
Can I use this for a child?
No. Child BMI is interpreted with age- and sex-specific charts. Use a paediatric or clinical tool for anyone under 18.
Why does it show 0 or nothing?
Weight or height is missing or zero. Enter both in the chosen unit system.
Is this medical advice?
No. This is an informational calculator only. For diagnosis or treatment, see a healthcare provider.

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