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BMI calculator

Compute your Body Mass Index and weight category.

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Body Mass Index (BMI) estimates whether your weight is healthy for your height. It is calculated by dividing your weight in kilograms by the square of your height in metres (kg/m²). Use it as a quick, free screening tool — not a full medical diagnosis.

How to use it

  1. Enter your weight in kilograms.
  2. Enter your height in centimetres.
  3. Read your BMI and weight category instantly.

Frequently asked questions

What is a healthy BMI?

A BMI between 18.5 and 24.9 is considered healthy for most adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or more is obese.

Is BMI accurate?

BMI is a useful screening tool but it doesn't measure body fat directly. It can misclassify very muscular people or the elderly, so treat it as a starting point and consult a health professional for a full assessment.

Does BMI work for athletes or muscular people?

Not always. Muscle weighs more than fat, so athletes can have a high BMI while being very lean. For them, body-fat percentage is a better measure.

What's the difference between BMI and body fat?

BMI uses only height and weight, while body-fat percentage estimates how much of your weight is actually fat. Two people with the same BMI can have very different body compositions.

How can I lower my BMI?

Combine a moderate calorie deficit with regular physical activity. Even losing 5–10% of your body weight can move your BMI toward a healthier range. Aim for gradual, sustainable changes.

Is BMI calculated differently for men, women or children?

The formula is the same for adult men and women. For children and teenagers, BMI is interpreted with age- and sex-specific percentiles instead of the fixed adult categories.

What does the BMI calculator actually compute?

It takes Weight (kg) and Height (cm) and derives BMI and Category from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

2 values: Weight (kg) and Height (cm). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Weight (kg) = 70 and Height (cm) = 175, the calculator returns BMI = 22.857 and Category = normal. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Weight (kg) = 77 and Height (cm) = 193 instead, BMI goes from 22.857 to 20.672 — which is why it is worth testing a few scenarios rather than trusting a single figure.

Further reading

All guides →
ExplainerIs BMI Reliable? The Limitations of Body Mass IndexBMI is a quick screen, not a diagnosis. Learn what it misses — muscle, fat distribution, age — and what to check alongside it.ExplainerWhat Is a Healthy BMI?BMI groups weight into ranges relative to height. Here's what counts as healthy, how to calculate it, and the limits of the number.ExplainerWhat Is a Child Growth Percentile?Growth percentiles compare a child's height and weight to others the same age and sex. Here's how to read them and what really matters.How-toHow to Find Your Target Weight for a Healthy BMIThe healthy BMI band of 18.5–24.9 turns into a weight range once you know your height. Here is how to work out yours step by step.ExplainerWhat Is a Healthy Waist-to-Height Ratio?Keeping your waist under half your height is a simple health marker. Learn what waist-to-height ratio means, how to measure, and why under 0.5 is the goal.ExplainerWhat Is Your Ideal Weight?There's no single ideal weight — it's a healthy range. Here's what the common formulas say, what they miss, and better ways to judge a healthy weight.