BMI Calculator
Calculate your Body Mass Index instantly.
Answer common BMI questions in plain language.
My weight is kg and my height is cm
I weigh lbs and I am ft in tall
BMI Categories (WHO Standard)
Underweight BMI < 18.5
Normal weight BMI 18.5–24.9
Overweight BMI 25–29.9
Obese BMI 30+
Source: WHO. Consult a healthcare professional.
BMI Explained
What is BMI and how is it calculated?
Body Mass Index is derived from weight and height as a body fatness screening indicator.
Metric: BMI = weight (kg) ÷ height² (m)
Example: 70 ÷ (1.75)² = 22.9
Imperial: BMI = (lbs ÷ height² (in)) × 703
Example: (154 ÷ 69²) × 703 = 22.7
Example: 70 ÷ (1.75)² = 22.9
Imperial: BMI = (lbs ÷ height² (in)) × 703
Example: (154 ÷ 69²) × 703 = 22.7
What do the BMI categories mean?
UnderweightBMI < 18.5
May indicate insufficient nutrition or other conditions.
Normal weightBMI 18.5–24.9
Lowest statistical health risk for most adults.
OverweightBMI 25–29.9
Increased risk of cardiovascular disease and type 2 diabetes.
Obese Class I–IIIBMI 30+
High to extremely high health risk. Medical guidance strongly recommended.
How to calculate target weight for a given BMI
Target weight (kg) = Target BMI × height² (m)
Height 175 cm, target BMI 22:
22 × (1.75)² = 67.4 kg
Height 175 cm, target BMI 22:
22 × (1.75)² = 67.4 kg
~7,700 kcal deficit/surplus ≈ 1 kg. Sustainable rate: 0.5–1 kg/week.
Limitations of BMI — when is it inaccurate?
- Athletes: High muscle raises BMI despite low body fat.
- Elderly: Muscle loss can mask high body fat at normal BMI.
- Pregnancy: Not applicable during pregnancy.
- Children: Use age/sex-specific percentile charts.
- South/East Asian adults: WHO recommends overweight threshold ≥23.
How to convert between metric and imperial
lbs → kg: ÷ 2.20462 | kg → lbs: × 2.20462
cm → in: ÷ 2.54 | in → cm: × 2.54
ft+in → cm: (ft × 30.48) + (in × 2.54)
cm → in: ÷ 2.54 | in → cm: × 2.54
ft+in → cm: (ft × 30.48) + (in × 2.54)