Health & Fitness
BMI Calculator – Check Your Body Mass Index Instantly
Use our free BMI Calculator to quickly find your Body Mass Index and check if you're underweight, healthy, overweight, or obese. Fast and accurate results.
What Is BMI and How Is It Calculated?
Body Mass Index (BMI) is a screening tool that estimates body fat using your height and weight. The formula is: BMI = weight (kg) ÷ height (m)². A BMI of 22.0 means you weigh 22 kg for every square meter of height. The WHO classifies adults into four categories: underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30).
BMI is not a diagnostic tool — it doesn't measure body fat directly or account for muscle mass, bone density, age, sex, or fat distribution. Athletes may have a high BMI due to muscle, not fat. Use BMI as a starting point, then consider waist circumference, body fat percentage, and other health markers for a complete picture.
BMI Scale
FAQ – BMI Calculator
What is BMI and how is it calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in meters squared: BMI = kg ÷ m². For example, a person weighing 70 kg at 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9. In imperial units: BMI = (weight in lbs × 703) ÷ (height in inches)².
What is a healthy BMI range?
The WHO defines a healthy BMI as 18.5–24.9 for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese. The optimal BMI for lowest mortality risk is around 20–25.
Is BMI the same for men and women?
The formula is identical, but interpretation differs. Women naturally carry more body fat (20–25% healthy) than men (10–20% healthy) at the same BMI.
Can BMI be inaccurate?
Yes. Athletes may be classified as "overweight" due to muscle mass. Elderly people may have a "normal" BMI but high body fat due to muscle loss. BMI doesn't account for fat distribution.
Does age affect BMI interpretation?
For adults 20+, the same BMI categories apply. For children and teens (ages 2–19), BMI is plotted on age-and-sex-specific growth charts as a percentile.
What is the ideal BMI?
Research suggests a BMI of 21–23 is associated with the lowest health risks. However, "ideal" depends on age, sex, muscle mass, ethnicity, and overall health.
How does BMI relate to body fat percentage?
Roughly: BMI 18.5 ≈ 10–20% body fat, BMI 25 ≈ 20–30%, BMI 30 ≈ 25–35%. Women typically have 5–10% more body fat than men at the same BMI.
Why is waist circumference important alongside BMI?
A waist over 40 inches (102 cm) for men or 35 inches (88 cm) for women indicates increased risk for heart disease and type 2 diabetes — even if BMI is "normal".
Do different ethnicities have different BMI thresholds?
Yes. The WHO suggests lower cutoffs for Asian populations: overweight at BMI 23+ and obese at 27.5+.
How can I improve my BMI?
To lower BMI: moderate calorie deficit (300–500 cal/day), 150+ min/week exercise, more protein and fiber. To raise BMI: increase calorie intake with nutrient-dense foods, add strength training.