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Check your Body Mass Index instantly. Get WHO-standard categories, a visual range chart, and personalized health context.
Enter your weight and height
to see your BMI evaluation
Hundreds of BMI tools exist. Most return a single number and leave you with questions. This free BMI Calculator gives you your result instantly, maps it against WHO-standard categories, and provides personalized health context.
Women naturally carry a higher percentage of body fat than men at the same BMI score. A BMI of 21 for a woman aged 30 is solidly Normal. Clinicians may interpret results differently for women over 50 due to postmenopausal shifts.
Men typically carry more muscle mass, which can sometimes overstate body fat percentage in athletic individuals. A BMI of 22–24 represents the center of the healthy range for men.
For adults, WHO standard ranges apply. However, for children and teenagers, BMI is interpreted entirely differently using age- and sex-specific percentile charts established by the CDC.
| BMI Range | Category | Health Signal |
|---|---|---|
| Below 18.5 | Underweight | May indicate nutritional deficiency. |
| 18.5 – 24.9 | Normal Weight | Lowest risk for health conditions. |
| 25.0 – 29.9 | Overweight | Elevated risk for cardiovascular issues. |
| 30.0 and above | Obese | High risk for diabetes and hypertension. |
BMI is accurate as a population screening tool but imprecise as an individual diagnostic. It does not differentiate fat from muscle and does not identify fat distribution (visceral vs subcutaneous). Use it as a directional signal and discuss results with your healthcare provider.
A BMI calculator computes your Body Mass Index using your height and weight. Using the formula BMI = weight (kg) ÷ height (m)² (or the imperial equivalent), it produces a number that the World Health Organization maps to one of four categories: Underweight (below 18.5), Normal (18.5-24.9), Overweight (25-29.9), or Obese (30+).
The mathematical formula for BMI is identical for men and women. However, the clinical interpretation differs. Women naturally carry a higher percentage of body fat than men at the same BMI score due to biological differences in body composition.
According to the WHO standard, a healthy BMI for adult women is 18.5 to 24.9. A BMI below 18.5 is classified as Underweight, 25-29.9 as Overweight, and 30 or above as Obese.
To calculate BMI in metric units: (1) Convert your height from centimeters to meters by dividing by 100. (2) Square that height value. (3) Divide your weight in kilograms by that squared height value.
For anyone under 20 years old, the result must be interpreted using CDC age- and sex-specific percentile charts — not the standard adult cutoff numbers. Pediatric BMI results should always be reviewed with a qualified healthcare provider.