BMI Calculator

Units
Your BMI will appear here.
Underweight< 18.5
Normal weight18.5–24.9
Overweight25.0–29.9
Obesity class I30.0–34.9
Obesity class II35.0–39.9
Obesity class III≥ 40

Based on WHO BMI classification. This is a screening tool and doesn’t account for muscle mass or body composition.

Info

BMI — What it is

Body Mass Index (BMI) is a simple screening number comparing weight and height to estimate if your body weight is in a typical health range. It’s only a screening tool — not a full health diagnosis and does not directly measure fat or muscle.

Discuss your BMI results with a healthcare professional for personalized insight.

Calculator

How the calculator works

  1. Choose Metric or Imperial units.
  2. Enter your height and weight in the corresponding fields.
  3. Click Calculate to see your BMI and WHO category.
  4. Use Copy or Share to save or send results.
  5. Press Clear to reset the form.
Ruler

Units

  • Metric: height in centimeters, weight in kilograms.
  • Imperial: height in feet/inches, weight in pounds.
  • Choose the system you use daily to avoid input errors.

Tip: Only fields related to your chosen unit are shown to keep it simple.

Formula

Formulas

Metric

BMI = weight(kg) ÷ (height(m))²

Example: 65 ÷ (1.70 × 1.70) = 22.5

Imperial

BMI = 703 × weight(lb) ÷ (height(in))²

Example: 143 lb, 67 in → 703 × 143 ÷ 4489 = 22.4

Table

WHO BMI Categories

Category
BMI (kg/m²)
Underweight
< 18.5
Normal weight
18.5–24.9
Overweight
25.0–29.9
Obesity class I
30.0–34.9
Obesity class II
35.0–39.9
Obesity class III
≥ 40

WHO ranges are population-based and may differ by region or ethnicity.

Lightbulb

Helpful tips

  • Measure height without shoes, standing straight.
  • Weigh yourself at a consistent time for accuracy.
  • Use one measurement system only.
  • Double-check inputs if BMI seems off.
Warning

Common mistakes

  • Mixing cm with pounds or ft with kg.
  • Forgetting inches when entering height.
  • Rounding height too much — small changes affect BMI.
Help

Frequently asked questions

Is BMI accurate for athletes?

Not always. Muscular people may have a higher BMI despite low fat levels. Consider waist size and body fat tests.

Does BMI differ by age or gender?

For adults, categories are the same. For children and teens, BMI is adjusted for age and sex using percentiles.

What if my BMI is near a category limit?

Minor measurement differences can shift your result. Use it as a guide, not a final diagnosis.

Can BMI alone determine health?

No. BMI is just one indicator. Lifestyle, activity level, and overall health matter more.

Disclaimer: BMI is a general indicator and does not directly measure body fat, muscle, or overall health. Consult a healthcare provider for personalized assessment.