BMI Calculator

Enter your weight and height to calculate your Body Mass Index.

kilograms

centimetres

Please enter valid weight and height values.

Your BMI
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What is BMI?

Body Mass Index (BMI) is a simple screening measurement that estimates whether your weight is in a healthy range for your height. It is calculated by dividing your weight in kilograms by the square of your height in metres (kg/m²). Because it needs only two easy-to-measure numbers, BMI has been used by doctors, researchers, and health organisations worldwide for decades as a quick, low-cost indicator of weight status across large populations.

How is BMI calculated?

The formula is straightforward:

  • BMI = weight (kg) ÷ height (m)²

For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 ≈ 22.9, which falls in the normal weight range. This calculator does the maths for you instantly — just enter your weight in kilograms and your height in centimetres.

BMI categories for adults

The World Health Organization (WHO) defines these standard BMI ranges for adults aged 20 and over:

  • Under 18.5 — Underweight
  • 18.5 to 24.9 — Normal weight
  • 25.0 to 29.9 — Overweight
  • 30.0 and above — Obese

The limitations of BMI

BMI is a useful starting point, but it is not a perfect measure of health or body fat. It does not distinguish between muscle and fat, so very muscular people — such as athletes and weightlifters — can have a high BMI while carrying very little body fat. It also does not account for where fat is stored, bone density, age, sex, or ethnicity. Older adults may have more body fat than a younger person with the same BMI, and some populations have different health risks at the same BMI value. For these reasons, BMI is best used alongside other measurements such as waist circumference, body-fat percentage, and a conversation with a healthcare professional.

How to use your result

Treat your BMI as one data point, not a verdict. If your result falls outside the normal range, it can be a helpful prompt to look at your overall habits — nutrition, activity, sleep, and stress — rather than a reason to panic. Small, consistent changes are far more effective than drastic short-term measures. If you are concerned about your weight or health, speak to a doctor or registered dietitian who can assess your individual situation.

Frequently asked questions

What is a healthy BMI?

For most adults, a BMI between 18.5 and 24.9 is considered the healthy or "normal weight" range. However, a healthy weight varies between individuals depending on muscle mass, body composition, and other factors, so the range is a guide rather than a strict rule.

Is BMI accurate?

BMI is accurate as a population-level screening tool and a quick estimate for the average person, but it can be misleading for individuals with high muscle mass, athletes, pregnant people, the elderly, and children. It estimates weight status, not body-fat percentage or overall health, so it should not be used in isolation.

Does muscle affect BMI?

Yes. Muscle is denser than fat, so a very muscular person can have a BMI in the "overweight" or even "obese" range while having low body fat and excellent health. This is one of the main limitations of BMI and why it should be combined with other measures.

Is BMI calculated differently for men and women?

No — the BMI formula is identical for men and women. However, at the same BMI, women tend to have more body fat than men on average, so the same number can mean slightly different things depending on sex.

Can I use this calculator for children?

This calculator uses the adult BMI categories, which are not appropriate for children and teenagers. For people under 20, BMI is interpreted using age- and sex-specific percentile charts. Consult a paediatrician or use a dedicated child BMI percentile tool instead.

Disclaimer: This BMI calculator is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with any questions about your health.

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