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Health Intelligence

Know your
Body Mass
Index

The world's most-used health screening metric — calculated instantly from your height and weight. Free, accurate, no account needed.

Metric & Imperial WHO standard Ideal weight included
Under Normal Over Obese HEALTHY RANGE 18.5 – 24.9 YOUR BMI —
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BMI Calculator

Enter your height and weight below

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Body Mass Index
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Underweight
<18.5 Normal
18.5–24.9 Overweight
25–29.9 Obese
≥30

BMI is a population-level screening tool and does not account for muscle mass, age, sex, or body composition. Always consult a qualified health professional for personalised advice.

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BMI scale at a glance

Under Normal Over Obese Body Mass Index Scale
Under <18.5
Normal 18.5–24.9
Overweight 25–29.9
Obese ≥30

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Did you know?

BMI was invented by Belgian mathematician Adolphe Quetelet in the 1830s — nearly 200 years ago — long before modern body composition science existed.

It wasn't originally designed as a health tool, but as a statistical description of population averages.

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Your BMI score, category, and ideal weight range
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Visual scale shows where you fall among categories

What is BMI?

Body Mass Index is a simple numerical value calculated from your height and weight. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, it is used today as a quick population-level screening tool for weight categories associated with health risk.

The formula is: BMI = weight (kg) ÷ height² (m²). Despite its age, BMI remains the most widely used clinical screening metric because it requires no special equipment and correlates reasonably well with body fat percentage at the population level.

BMI categories

CategoryBMI rangeRisk level
UnderweightBelow 18.5Increased nutritional risk
Normal weight18.5 – 24.9Lowest health risk
Overweight25.0 – 29.9Moderately increased risk
Obese30.0 and aboveHigh to very high risk

Limitations of BMI

While BMI is a useful screening tool at the population level, it has well-known limitations for individuals. It cannot distinguish between fat and muscle — a highly muscular athlete may have a "high" BMI while having very low body fat. It also does not account for how fat is distributed in the body, which matters significantly for health risk.

For a more complete picture of your body composition, use BMI alongside our Body Fat Calculator and your waist circumference. Always discuss results with a healthcare professional.

BMI accuracy by group

BMI correctly classifies excess body fat in roughly 50–70% of individuals. It is less reliable for athletes, elderly adults, pregnant women, and people of South Asian or East Asian descent, where a lower overweight threshold of 23.0 is sometimes recommended by health organisations.

Frequently asked questions

BMI is a reasonable proxy for body fatness at the population level, correctly classifying excess body fat in roughly 50–70% of individuals. At the individual level, accuracy varies. It is less reliable for athletes (who may be misclassified as overweight), older adults, and people of certain ethnicities. Use it as a starting point, not a definitive verdict.
The standard BMI formula and categories are identical for adult men and women. However, women naturally carry more body fat at the same BMI due to physiological differences. Some researchers argue for sex-specific cut-offs, but the WHO standard categories remain the most widely used clinical reference worldwide.
The WHO defines 18.5–24.9 as normal weight — the range associated with the lowest overall health risk in adult populations. For South or East Asian descent, some organisations recommend a lower overweight threshold of 23.0, due to higher metabolic risk at lower BMI values in these populations.
In metric: BMI = weight (kg) ÷ height² (m²). Example: 70 kg and 1.75 m = 70 ÷ 3.0625 = 22.9. In imperial: BMI = (weight in lb × 703) ÷ height² (in inches). Example: 154 lb and 5'9" (69 in): (154 × 703) ÷ 4761 = 22.7.