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?
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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