Free Online BMI Calculator
100% Free, Browser-Based Body Mass Index & Healthy Weight Calculator.
Your BMI
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kg/m²
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Body fat (est.)
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New BMI
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Ponderal index
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To healthy range
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BMI 18.5 – 24.9 for —
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Maximum
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Classic clinical formulas for men
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Medical disclaimer: BMICalculator is for educational and informational purposes only. BMI is a population-level screening measure and does not diagnose health conditions or measure body fat directly. Always consult a qualified healthcare professional before making decisions about diet, exercise or treatment.
These World Health Organization classifications apply to adults aged 20 and over, for both men and women. Your current category is highlighted.
| Category | BMI (kg/m²) | BMI Prime | Health risk |
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Body Mass Index divides your weight by the square of your height:
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = 703 × weight (lb) ÷ height (in)²
Example: 70 kg at 1.75 m → 70 ÷ 3.0625 = 22.9 (Normal weight).
The BMI equation and adult cut-offs are the same for everyone. What differs is body composition: at an identical BMI, women typically carry around 10–12 percentage points more body fat than men, and older adults carry more fat than younger ones. That is why this tool uses your sex and age for the estimated body-fat figure (Deurenberg equation) and for the ideal-weight formulas.
BMI Prime = BMI ÷ 25. A value of 1.00 sits exactly at the upper healthy limit; 0.74–0.99 is the normal zone. Your healthy weight range is the weight that gives a BMI of 18.5 to 24.9 at your height: 18.5 × height(m)² to 24.9 × height(m)².
Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964) estimate ideal body weight from height over 5 feet, originally for medication dosing. They differ by a few kilograms, so treat the spread as a reference band rather than an exact target.
For most adults aged 20 and over, a BMI between 18.5 and 24.9 is considered a healthy (normal) weight. Below 18.5 is underweight, 25.0–29.9 is overweight, and 30.0 or higher is classed as obesity (Class I: 30–34.9, Class II: 35–39.9, Class III: 40+).
BMI uses the same formula for men and women: weight in kilograms divided by height in meters squared (kg/m²). In imperial units it is 703 × weight in pounds ÷ height in inches squared. The adult category cut-offs are identical for both sexes, although women typically carry more body fat than men at the same BMI.
BMI does not measure body fat directly and cannot distinguish muscle from fat, so muscular athletes may be classed as overweight. It ignores fat distribution (waist size), bone density, age-related muscle loss, pregnancy and ethnic differences — some Asian populations face higher health risks at lower BMI values. It is a screening tool, not a diagnosis.
BMI Prime is your BMI divided by 25, the upper limit of the normal range. A BMI Prime between 0.74 and 1.00 corresponds to a healthy weight; 1.20 means you are 20% above the upper healthy limit.
Multiply your height in meters squared by 18.5 for the minimum and by 24.9 for the maximum healthy weight. For example, at 1.75 m the healthy range is about 56.7 kg to 76.3 kg (125 to 168 lbs). BMICalculator shows this range automatically for your height.
For ages 2 to 19, BMI is calculated the same way but interpreted with age- and sex-specific BMI-for-age percentile charts (such as CDC or WHO growth charts), not the adult categories. Adult cut-offs shown for younger ages are for reference only.
A BMI of 30.0 or higher is classified as obesity in adults. It is divided into Class I (30.0–34.9), Class II (35.0–39.9) and Class III (40.0 and above), sometimes called severe obesity.
Yes. BMICalculator runs 100% in your browser with JavaScript. Your height, weight, age and sex are never uploaded, stored on a server or tracked.