BMI Calculator
Calculate your Body Mass Index (BMI) to assess whether your weight falls within a healthy range. Useful for nutrition planning, fitness goal-setting, and health screening.
About this calculator
Body Mass Index (BMI) is a widely used screening metric that relates body weight to height squared. The formula is: BMI = weight (kg) / (height (m))². Because height is often entered in centimeters, it must first be converted to meters by dividing by 100, giving: BMI = weight / (height / 100)². The resulting number is interpreted against standard WHO ranges: below 18.5 is underweight, 18.5–24.9 is normal weight, 25–29.9 is overweight, and 30 or above is obese. BMI is a population-level tool and does not account for muscle mass, bone density, or fat distribution, so it is best used as a starting point for nutrition and health planning rather than a definitive diagnosis.
How to use
Suppose you weigh 75 kg and are 175 cm tall. First, convert height to meters: 175 / 100 = 1.75 m. Then square it: 1.75² = 3.0625. Finally, divide weight by that value: 75 / 3.0625 = 24.49. Your BMI is approximately 24.5, which falls in the 'Normal weight' range (18.5–24.9). If your weight were 90 kg at the same height: 90 / 3.0625 = 29.4, placing you in the 'Overweight' category and signaling a need to review calorie intake.
Frequently asked questions
What is a healthy BMI range for adults?
The World Health Organization defines a healthy BMI as 18.5 to 24.9 for adults. A BMI below 18.5 is classified as underweight, 25–29.9 as overweight, and 30 or above as obese. These thresholds are the same for both men and women in the standard adult scale, though some health authorities use slightly different cut-offs for certain ethnic groups. Keep in mind that BMI is a screening tool, not a direct measure of body fat or metabolic health.
Why is BMI not always accurate for athletes and muscular people?
BMI uses only weight and height, so it cannot distinguish between lean muscle mass and body fat. An athlete with high muscle mass may register an 'overweight' BMI despite having a low body fat percentage, because muscle is denser and heavier than fat. Conversely, someone with a normal BMI could still have excess visceral fat if they have low muscle mass. For athletes, measures like body fat percentage, waist-to-hip ratio, or DEXA scans provide a more accurate picture of body composition.
How does BMI relate to nutrition and calorie planning?
BMI provides a starting reference point for estimating whether your current weight is appropriate for your height, which informs calorie targets for weight loss, gain, or maintenance. If your BMI indicates you are overweight, a modest calorie deficit (300–500 kcal/day) combined with balanced macros is a common starting strategy. If underweight, a calorie surplus with adequate protein supports healthy weight gain. BMI alone does not prescribe how many calories to eat — it is best paired with a TDEE or macro calculator for actionable nutrition planning.