BMI Calculator
Calculate your Body Mass Index and see which WHO weight category it falls into.
How to use the bmi calculator
- Choose metric or imperial units.
- Enter your weight and height.
- Click Calculate to get your BMI and category.
What BMI is good for
BMI is a quick population-level screening tool for under- and over-weight, not a diagnosis. It works best alongside measures of body composition and waist circumference.
What BMI does and does not measure
BMI is simply weight divided by height squared, a quick population-level screen for weight category. It does not distinguish muscle from fat, so a muscular athlete can register as 'overweight' despite low body fat.
Use BMI as a rough first check, not a diagnosis. For individuals, body-fat percentage and waist measurements tell a more meaningful story about health.
BMI categories and their limits
The WHO bands (under 18.5 underweight, 18.5-24.9 normal, 25-29.9 overweight, 30+ obese) are useful for tracking populations and trends. For athletes, older adults, and some ethnic groups, the cut-offs are less accurate, which is why clinicians pair BMI with other measures rather than relying on it alone.
WHO BMI categories
| BMI | Category | What it suggests |
|---|---|---|
| Below 18.5 | Underweight | May reflect under-nutrition; worth reviewing if unintentional |
| 18.5–24.9 | Normal weight | Associated with the lowest health risk for most adults |
| 25.0–29.9 | Overweight | Raised risk, though fitness and body composition matter a great deal |
| 30.0–34.9 | Obese (class I) | Higher risk of metabolic and cardiovascular conditions |
| 35.0–39.9 | Obese (class II) | Substantially higher health risk |
| 40.0 and above | Obese (class III) | Highest-risk category; medical guidance advised |
These cut-offs describe populations, not individuals. Some ethnic groups carry higher risk at lower BMIs, which is why several health bodies use a 23 overweight threshold for South Asian and East Asian populations.
Healthy weight range by height (BMI 18.5–24.9)
| Height | Healthy weight range |
|---|---|
| 155 cm (5 ft 1 in) | 44–60 kg |
| 160 cm (5 ft 3 in) | 47–64 kg |
| 165 cm (5 ft 5 in) | 50–68 kg |
| 170 cm (5 ft 7 in) | 53–72 kg |
| 175 cm (5 ft 9 in) | 57–76 kg |
| 180 cm (5 ft 11 in) | 60–81 kg |
| 185 cm (6 ft 1 in) | 63–85 kg |
| 190 cm (6 ft 3 in) | 67–90 kg |
Each range is BMI 18.5 to 24.9 at that height. Muscular, athletic builds often sit above the top of the range while carrying low body fat, so read it alongside a body-fat or waist measurement rather than on its own.
Frequently asked questions
How is BMI calculated?
BMI equals your weight in kilograms divided by your height in metres squared. A 75 kg person who is 1.78 m tall has a BMI of about 23.7.
Is BMI accurate for athletes?
Not very. BMI cannot tell muscle from fat, so muscular athletes often score as overweight despite low body fat. Pair it with body-fat or waist measures.
Is BMI accurate for athletes?
Often not. Because BMI cannot tell muscle from fat, lean, muscular people are frequently misclassified as overweight. Body-fat percentage is more informative for them.
What is a healthy BMI range?
The WHO considers 18.5-24.9 the normal range for most adults, but it is a screening tool, not a complete picture of health.
Should I worry if my BMI is slightly high?
A slightly high BMI with good fitness, a healthy waist measurement, and normal blood markers is usually less concerning than BMI alone suggests. Discuss persistent concerns with a clinician.
What is a healthy weight for my height?
The healthy-weight table below converts the normal BMI band (18.5–24.9) into a weight range for common heights — for example, roughly 53–72 kg at 170 cm. Treat it as a screening guide rather than a target, since athletic builds can sit above it with low body fat.
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