Check your Body Mass Index and weight category in metric or imperial units.
Health figures are processed locally and never stored.
How is BMI calculated?
BMI = weight (kg) ÷ height (m)². In imperial units, BMI = 703 × weight (lb) ÷ height (in)². The result classifies weight as underweight (below 18.5), normal (18.5–24.9), overweight (25–29.9) or obese (30+). BMI is a screening estimate and does not directly measure body fat or account for muscle mass.
Understanding your result
BMI is a population-level screening tool, not a diagnosis. It does not distinguish muscle from fat and may misclassify very muscular or older individuals. Use it as a general guide alongside professional advice.
Formula and method
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)². Standard adult categories: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese.
Assumptions and limitations
BMI is a general screening estimate, not medical advice or a diagnosis. It relies only on height and weight, so it cannot separate muscle from fat or account for age, sex, frame or fat distribution. Results vary by individual and should be discussed with a health professional.
Worked example
A person 175 cm tall weighing 70 kg has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the normal range.
How to use this tool
- Choose metric or imperial units.
- Enter your height and weight.
- Press Calculate to see your BMI and category.
Common mistakes to avoid
- Entering height in centimetres while the metric formula expects metres internally (the tool converts for you).
- Treating BMI as a body-fat percentage — it is not.
About the BMI Calculator
Body Mass Index (BMI) is a simple screening number that relates weight to height. This calculator returns your BMI and the standard weight category in either metric or imperial units.
Who should use this tool
Adults who want a quick read on whether their weight sits in a healthy range, and anyone starting a fitness, diet or general-health routine.
Benefits
- Shows your BMI and weight category instantly.
- Supports both metric (cm/kg) and imperial (ft·in/lb) units.
- Processes your figures locally — nothing is stored or uploaded.
- Explains the result rather than just printing a number.
Practical use cases
- Checking whether your current weight is in the healthy range.
- Tracking changes in body weight over time as a rough guide.
- Preparing a baseline figure before speaking to a doctor or trainer.
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Frequently asked questions
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so very muscular people can show a high BMI while being healthy.
Does this work for children?
These categories are for adults. Children use age- and sex-specific percentile charts instead.
Is BMI the same for men and women?
The BMI formula and the standard adult categories are identical for men and women, so this tool applies one set of thresholds to both. Body composition differs between individuals, however, so read the number as a general guide rather than a precise measure of body fat.