Calculate your Body Mass Index (BMI) and understand your weight status with health recommendations.
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Based on BMI 18.5-24.9
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To reach normal BMI
BMI Prime
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Ponderal Index
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Body Surface Area
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Body Mass Index (BMI) is a measure of body fat based on height and weight. It's a useful screening tool but doesn't directly measure body fat or account for muscle mass.
Body Mass Index (BMI) is a screening measure that compares your weight to your height using the standard formula: BMI equals weight in kilograms divided by height in meters squared (kg/m²). If you enter imperial units, the calculator converts pounds to kilograms and feet and inches to meters before applying the same equation, so both unit systems produce identical results.
Alongside the raw score, the page maps your result onto the standard adult categories and derives the weight range that corresponds to a normal BMI for your height, plus how many kilograms or pounds you would need to gain or lose to reach it. Three supplementary metrics round out the picture: BMI Prime (your BMI divided by 25), the Ponderal Index (weight divided by height cubed), and Body Surface Area estimated with the Du Bois formula.
BMI is a quick screening tool, not a diagnosis. It cannot distinguish muscle from fat, so muscular people are routinely classed as overweight, and it says nothing about where fat is stored, which matters for health risk. It is not valid for children and teenagers, who need age-specific percentile charts. For a body-composition view, pair this with our body fat calculator, or compare targets with the ideal weight calculator.
Not really. BMI only uses height and weight, so it cannot tell the difference between muscle and fat. Athletes with large muscle mass often score in the overweight range despite low body fat. A waist measurement or a body fat estimate such as the US Navy method is usually more informative for this group.
For most adults, a BMI between 18.5 and 24.9 is classified as normal weight. Values below 18.5 suggest underweight, 25 to 29.9 overweight, and 30 or above obesity. These are screening thresholds, not diagnoses; a clinician will weigh other factors before drawing conclusions.
The formula is identical for both sexes: weight divided by height squared. Average body composition differs between men and women, but the standard cutoffs are applied to everyone. Some health organizations recommend lower overweight thresholds for certain Asian populations.
No. Body composition changes constantly as young people grow, so BMI must be plotted on age- and sex-specific percentile charts rather than compared with fixed adult categories. For anyone under 20, use CDC growth charts or consult a pediatrician.
BMI Prime is your BMI divided by 25, the upper limit of the normal range, so any value under 1.0 means you sit inside that range. The Ponderal Index divides weight by height cubed instead of squared, which some researchers consider more proportionate for very tall or very short people.