BMI calculator

Body Mass Index (BMI) calculator

Enter your height and weight to see your BMI and a rough category. This is a simple estimate, not medical advice.

Units

Height (cm)

Weight (kg)

Enter your details and click Calculate.

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Your BMI will appear here.

Typical adult categories (WHO): underweight < 18.5 · normal 18.5–24.9 · overweight 25–29.9 · obese ≥ 30. Always talk to a health professional for personalised advice.

How this BMI calculator works

BMI (Body Mass Index) is a ratio of weight to height. It’s often used as a quick screening metric, but it doesn’t diagnose health on its own.

The formula

Metric: BMI = weight (kg) ÷ height² (m²)

US/Imperial: BMI = 703 × weight (lb) ÷ height² (in²)

How to interpret results

BMI categories vary slightly by organization and population. Use BMI as a starting point and consider other factors (age, muscle mass, medical history).

FAQ

Why can BMI be misleading?

BMI doesn’t distinguish between muscle and fat, and it doesn’t account for body composition. Athletes and older adults can get “odd” results.

Should I use BMI for kids/teens?

For children and teens, BMI is typically interpreted using age/sex percentiles. This tool is aimed at adults.

What BMI is (and isn’t)

BMI (Body Mass Index) is a quick screening metric that compares weight to height. It’s useful for population‑level trends, but it can be misleading for individuals (for example: very muscular people, older adults, and some medical conditions).

Formula and categories

Metric: BMI = weight (kg) ÷ height (m)²

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

Common adult categories: under 18.5 (underweight), 18.5–24.9 (healthy range), 25–29.9 (overweight), 30+ (obesity).

Worked examples

Metric: 175 cm and 70 kg → BMI ≈ 22.9

Imperial: 5′9″ and 154 lb → BMI ≈ 22.7

Quick FAQ

Is BMI a diagnosis? No. It’s a screening number. If you’re concerned, use it as a starting point for a conversation with a clinician.

Why does BMI feel “wrong” for athletes? BMI can’t separate muscle from fat, so higher muscle mass can increase BMI even with low body fat.

Does BMI change if I use shoes or different units? Small measurement changes (especially height) can move BMI noticeably. Measure height/weight consistently.

How to use BMI responsibly

Track trends over time (weeks/months), not day‑to‑day fluctuations.
Use BMI alongside other measures (waist measurement, fitness, labs) if available.
For children/teens, BMI interpretation usually uses age‑ and sex‑based percentiles (adult categories may not apply).

Body Mass Index (BMI) calculator

How this BMI calculator works

The formula

How to interpret results

FAQ

What BMI is (and isn’t)

Formula and categories

Worked examples

Quick FAQ

How to use BMI responsibly

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