Body Mass Index, calculated as weight (kg) / height (m)2. It is a population-level screen, not a body-composition measurement.

BMI Calculator

Body Mass Index, ideal weight, body fat, calorie needs and health-risk assessment with metric or imperial units.

Measurements

Height

Weight

Personal Info (for advanced metrics)

Age

yrs

Sex

Activity Level

Goal

Body Measurements (optional - improves body fat estimate)

Waist

Hip

Neck

Enter your measurements
and press Calculate

BMI Score

Underweight Normal Overweight Obese I Obese II+

1618.525303540+

Ideal Weight Range

BMI 18.5 - 24.9

Est. Body Fat

Deurenberg formula

Lean Body Mass

Fat-free body mass

BMI Prime

Ratio to upper normal (1.0 = 25)

Daily Calorie Needs

BMR - Basal metabolic rate

TDEE - Total daily energy

Goal Target - -

Protein - 1.6 g/kg body weight

Alternate Weight Indices

Ponderal Index-kg/m³

BSA (Mosteller)-m²

Hamwi Ideal Wt-kg

Devine Formula-kg

Miller Formula-kg

Robinson Formula-kg

Health Risk Assessment

Export Results

About this calculator

WHO BMI Classification

Category	BMI (kg/m²)	Risk
Severe Thinness	< 16.0	Very High
Moderate Thinness	16.0 - 16.9	High
Mild Thinness	17.0 - 18.4	Moderate
Normal	18.5 - 24.9	Average
Overweight	25.0 - 29.9	Increased
Obese Class I	30.0 - 34.9	High
Obese Class II	35.0 - 39.9	Very High
Obese Class III	≥ 40.0	Extremely High

Formulas Used

BMI: weight(kg) / height(m)²
BMR (Mifflin-St Jeor): Male: 10W + 6.25H − 5A + 5
Female: 10W + 6.25H − 5A − 161
Body Fat (Deurenberg): 1.20 × BMI + 0.23 × Age − 10.8 × sex − 5.4
Body Fat (U.S. Navy): Men: 495 / (1.0324 − 0.19077 × log(W−N) + 0.15456 × log(H)) − 450
Women: 495 / (1.29579 − 0.35004 × log(W+H−N) + 0.22100 × log(H)) − 450
BSA (Mosteller): √(Height(cm) × Weight(kg) / 3600)
Ponderal Index: weight(kg) / height(m)³

BMI is a screening tool only. It does not diagnose body fatness or health. Consult a qualified healthcare professional for medical advice.

How to use

Choose metric (kg, cm) or imperial (lb, in) units.
Enter your height and weight.
Optionally add age, sex, activity level and body measurements for richer metrics.
Press Calculate. The BMI value, category and full breakdown appear instantly.
Compare your value to the WHO scale and review the healthy weight range.

Frequently asked questions

What is BMI exactly?

Body Mass Index, calculated as weight (kg) / height (m)². It is a population-level screen, not a body-composition measurement.

How accurate is BMI?

BMI works reasonably well as a screen for groups but can mislabel muscular individuals as overweight and very lean individuals as healthy. Pair it with waist circumference or a body-fat measurement for a fuller picture.

Why are the WHO ranges different from some local guidelines?

Some health authorities use slightly different cut-offs based on local population data, particularly for South and East Asian populations where health risks rise at lower BMIs.

Should children use this calculator?

No. For children and teens, BMI must be interpreted against age and sex percentile charts rather than the adult WHO ranges. Use a paediatric-specific tool.