BMI calculator
Calculate your body mass index and see your healthy weight range. Supports metric (cm/kg) and imperial (ft/lb) units.
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Worked example: 5'7", 154 lb
Imperial BMI formula: (weight in lb ÷ height in inches²) × 703.
- Height: 5'7" = 67 inches
- Weight: 154 lb
- Calculation: (154 ÷ 67²) × 703 = (154 ÷ 4,489) × 703
- BMI: 24.1 — right at the top of the "healthy weight" band (18.5–24.9)
In metric, the same person (170cm, 70kg) gets BMI = 70 ÷ 1.70² = 70 ÷ 2.89 = 24.2 — the tiny difference is just imperial-to-metric rounding.
BMI categories (WHO / NHS / CDC)
- Below 18.5 — Underweight
- 18.5 to 24.9 — Healthy weight
- 25 to 29.9 — Overweight
- 30 and above — Obesity
The marker on the scale above shows exactly where your result falls between these four bands.
These WHO/CDC/NHS thresholds are the standard used across most of the world, but not universal — several health agencies in parts of Asia use lower cutoffs (overweight from 23, obesity from 25) because research shows health risk at a given BMI tends to appear at lower thresholds in some Asian populations. If you fall outside these regions, the standard thresholds above are the right reference; otherwise check your local health authority's guidance.
Healthy weight range by height
The weight range that corresponds to a BMI of 18.5–24.9 at common heights.
| Height (metric) | Healthy weight | Height (imperial) | Healthy weight |
|---|---|---|---|
| 150 cm | 42–56 kg | 5'0" | 95–128 lb |
| 160 cm | 47–64 kg | 5'4" | 108–145 lb |
| 170 cm | 53–72 kg | 5'7" | 118–159 lb |
| 180 cm | 60–81 kg | 5'10" | 129–174 lb |
| 190 cm | 67–90 kg | 6'2" | 144–194 lb |
Use the calculator above for your exact height — this table is for a quick sanity check.
What BMI doesn't measure
BMI is a quick, free screening tool used by doctors worldwide because it correlates reasonably well with body fat at a population level — but it only uses height and weight, so it can't tell muscle from fat. A muscular athlete can show as "overweight" despite having low body fat, while someone with low muscle mass can have a "healthy" BMI but a high body fat percentage. See our BMI vs body fat comparison for a deeper look, and our ideal weight for your height guide for more context.
- Athletes and very muscular people — BMI often overestimates body fat.
- Older adults — BMI can underestimate body fat as muscle mass naturally declines with age.
- Pregnant women — weight gain is expected and healthy; BMI categories don't apply during pregnancy.
Waist circumference is a useful companion metric because it captures something BMI can't: where fat is carried. Two people with an identical BMI can have very different health risk profiles if one carries more weight around the abdomen — a pattern linked to higher cardiovascular and metabolic risk regardless of overall BMI. If your BMI is borderline or you want a fuller picture, pairing it with a waist measurement or our body fat calculator gives more context than BMI alone.
Frequently asked questions
What is a healthy BMI?
For most adults, 18.5 to 24.9 is considered healthy by the WHO, CDC and NHS.
How is BMI calculated?
Weight in kilograms divided by height in metres squared (kg/m²). In imperial: (lb ÷ in²) × 703.
Is BMI accurate for everyone?
It's a screening tool, not a diagnosis. Muscular athletes, older adults and pregnant women should interpret it with care.
What should I do if my BMI is outside the healthy range?
Treat it as a starting point for a conversation with a doctor or dietitian, not a verdict — they can assess body composition, health markers and context BMI can't see.
Does BMI apply the same way to men and women?
The formula and category thresholds are identical for both sexes. Women naturally carry a higher body fat percentage than men at the same BMI, which is one reason BMI alone can't distinguish body composition — see our BMI vs body fat comparison.
How does BMI work for children and teens?
It doesn't — this calculator is for adults 18 and over. Children and teens are assessed using age- and sex-specific BMI percentile charts, not the fixed adult categories used here, because healthy body composition changes throughout growth.
This tool is for information only and is not medical advice. Consult a health professional about your weight or health.