Enter your height and weight to get your BMI instantly, with the WHO category and your healthy weight range for your height.
How to use this calculator
Pick your unit system — metric (cm, kg) or imperial (ft/in, lb).
Enter your height. In imperial, fill feet and inches separately.
Enter your weight — the BMI, WHO category and healthy weight range update instantly.
Compare your current weight with the healthy range shown for your exact height.
Recheck after meaningful weight changes; BMI moves with weight, not with fitness alone.
Formula & method
How BMI is calculated
BMI = weight (kg) ÷ height (m)²
Imperial inputs are converted first: 1 ft = 30.48 cm, 1 in = 2.54 cm, 1 lb = 0.4536 kg. WHO ranges: under 18.5 underweight · 18.5–24.9 normal · 25–29.9 overweight · 30+ obese.
Example
Height 175 cm and weight 70 kg → BMI = 70 ÷ 1.75² = 22.9, which falls in the normal range (18.5–24.9).
Key insights
WHO adult ranges: below 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 and above obese — identical for men and women.
For a person of average height (1.75 m), a change of about 3 kg (6.6 lb) moves BMI by one full point.
BMI cannot tell muscle from fat: many muscular athletes read 'overweight' while being lean.
Waist circumference adds information BMI misses — abdominal fat carries risk even at a 'normal' BMI.
Children and teens are assessed with age- and sex-specific BMI percentiles, not these adult cut-offs.
How to interpret your result
In the normal range (18.5–24.9)
This band correlates with the lowest weight-related health risk for most adults. The goal is maintenance, not further loss.
Above 25
BMI is a screening flag, not a diagnosis. Body composition, waist size, blood pressure and blood work give the real picture — review them with a professional before acting.
Below 18.5
Unintentional low weight deserves medical attention. Deliberate weight gain works best through progressive resistance training plus adequate protein and calories.
The healthy weight range
It translates the 18.5–24.9 band into kilograms or pounds for your exact height — a more actionable target than the index itself.
Frequently asked questions
Is BMI accurate for everyone?
BMI is a screening tool, not a diagnosis. It can overestimate body fat in muscular people and underestimate it in older adults. Use it as a starting point, not a verdict.
What is a healthy BMI?
The WHO considers 18.5 to 24.9 a normal range for most adults. The calculator also shows the weight range that corresponds to this BMI band for your exact height.
Does BMI differ for men and women?
The standard formula and categories are the same for adult men and women. Children and teens use age- and sex-specific percentile charts instead.
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