BMI Calculator
This free BMI calculator converts your height and weight into Body Mass Index and the matching WHO weight category as you type, with a unit switch for metric (cm and kg) or imperial (feet plus inches and pounds) input.
How to use
- Choose metric (cm, kg) or imperial (ft+in, lb) units.
- Enter your height and weight — the BMI value appears immediately.
- Read the WHO category below the score: underweight, normal, overweight or obese.
- Adjust any number to compare scenarios; everything is computed on your device.
Frequently asked questions
How is BMI calculated?
BMI = weight (kg) / height (m)². Example: 65 kg at 1.70 m gives 65 / (1.70 × 1.70) ≈ 22.5. In imperial units the same result is weight (lb) / height (in)² × 703; this tool converts automatically when you switch unit systems.
What are the WHO BMI categories?
Below 18.5 is underweight, 18.5–24.9 is normal weight, 25–29.9 is overweight, and 30 or above is obesity. The boundaries are screening thresholds for populations, not individual diagnoses.
Why does a muscular person get a high BMI?
BMI only relates weight to height — it cannot tell muscle from fat. Athletes often land in the overweight range despite low body fat. Use BMI as a rough first signal, not a verdict on your health.
Is my height and weight uploaded anywhere?
No. The calculation runs entirely in your browser with plain client-side arithmetic. Your numbers never leave your device — nothing is stored, logged or uploaded.
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About this tool
This free BMI calculator converts your height and weight into Body Mass Index and the matching WHO weight category as you type, with a unit switch for metric (cm and kg) or imperial (feet plus inches and pounds) input. The formula is the standard one — BMI equals weight in kilograms divided by the square of height in meters — and the category follows WHO boundaries: under 18.5 underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, and 30 or above obesity. It is a useful first checkpoint for fitness plans, insurance paperwork and periodic health self-checks, and it takes seconds: type 170 cm and 65 kg and the result appears immediately. The calculation runs entirely in your browser, so your height and weight — data many people consider private — never leave your device; nothing is uploaded, logged or stored. BMI is a population-level screening measure, not a diagnosis of body fat or health: athletes with high muscle mass often read "overweight", and it does not distinguish fat distribution. Treat the number as a starting point and consult a professional for a full picture.