BMI Calculator
BMI is weight in kilograms divided by height in meters squared. At 70 kg and 175 cm, your BMI is 22.9 — in the normal range (18.5-25). BMI is a population-level screening tool, not a diagnosis: athletes and older adults often fall outside their true health range.
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How it works
BMI = weight (kg) ÷ height (m)². Categories: under 18.5 underweight, 18.5-24.9 normal, 25-29.9 overweight, 30+ obese. The World Health Organization uses these cutoffs for population screening — they were derived from large population studies, not individual health assessment.
Worked example
A person weighing 70 kg at 1.75 m: 70 ÷ (1.75 × 1.75) = 22.86 → normal weight. The same weight at 1.60 m: 70 ÷ 2.56 = 27.3 → overweight.
Assumptions
- Metric units: Calculated in kg and cm; 1 kg = 2.2046 lb, 1 cm = 0.3937 in
- Cutoffs: WHO categories used (18.5 / 25 / 30)
- Not a diagnosis: BMI doesn't distinguish muscle from fat or account for age, sex, or ethnicity
What the result means
Your category is a quick screen, not a verdict. High muscle mass can push athletes into 'overweight' despite low body fat; normal BMI can hide unhealthy fat distribution. For an individual picture, waist circumference and body-fat measurements matter more. If your BMI is outside the normal range, talk to a healthcare professional rather than self-diagnosing.
Frequently asked questions
What is a healthy BMI?
The WHO defines 18.5-24.9 as the normal range for adults. Below 18.5 is underweight, 25-29.9 overweight, 30+ obese — but these are screening cutoffs, not individual health verdicts.
Is BMI accurate for athletes?
No — BMI can't distinguish muscle from fat. A muscular athlete may show 'overweight' with very low body fat. Use waist circumference or body composition for a better picture.
How do I calculate BMI by hand?
Divide your weight in kilograms by your height in meters squared (weight ÷ height²). To use pounds and inches: 703 × weight(lb) ÷ height(in)².
Does BMI apply the same to men and women?
The same cutoffs are used for both sexes, though body-fat distribution differs. Some research suggests adjusted ranges could be more accurate, but WHO cutoffs remain the standard.
Is BMI a good indicator of health?
It's a useful quick screen and correlates with health risk at population level, but it misses muscle mass, fat distribution, and metabolic health. Use it as one data point, not a diagnosis.
This tool is for informational purposes only and is not medical advice. BMI is a screening measure with known limitations. Consult a healthcare professional for health assessment.