BMI Calculator - Calculate Your Body Mass Index
Calculate your Body Mass Index and understand your health category.
What Is BMI?
Body Mass Index (BMI) is a screening tool based on height and weight. It's used by doctors and health organizations worldwide to categorize weight status — underweight, normal, overweight, or obese. BMI does not measure body fat directly and doesn't diagnose health conditions, but it can flag whether further evaluation is worth considering.
How Is BMI Calculated?
The formula is the same for adults of any age or sex. This calculator uses the metric version only (kg and metres):
- Metric: BMI = weight (kg) ÷ height (m)²
- Imperial: BMI = 703 × weight (lb) ÷ height (in)²
BMI Categories
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Malnutrition, osteoporosis, weakened immunity |
| 18.5 – 24.9 | Normal weight | Lowest risk for weight-related disease |
| 25.0 – 29.9 | Overweight | Higher risk of heart disease, hypertension, type 2 diabetes |
| 30.0 and above | Obese | High risk of cardiovascular disease, diabetes, joint problems |
Limitations of BMI
- Doesn't measure body fat directly — it can't distinguish muscle from fat.
- May misclassify athletes — muscular people can have a high BMI but low body fat.
- Doesn't account for age, sex, or ethnicity — the same cutoffs are used for all adults.
- Not suitable for children or pregnant women — they need separate growth charts.
Frequently Asked Questions
What is a healthy BMI range for adults?
A healthy BMI for most adults is between 18.5 and 24.9. This range is linked with the lowest risk of weight-related diseases. However, BMI is only one measure — body fat percentage and waist circumference matter too.
Is BMI accurate for athletes and bodybuilders?
No — BMI often overestimates body fat in athletes because muscle is denser than fat. A muscular person can have a BMI over 25 while being very lean. For them, body fat percentage is a better indicator.
Can I use this BMI calculator for children?
No. Children and teens need age- and sex-specific BMI percentiles from growth charts. The adult categories in this calculator don't apply to anyone under 20. Talk to a pediatrician for accurate assessment.
Does BMI differ for men and women?
The formula and categories are the same for both sexes. However, women naturally tend to carry more body fat than men at the same BMI, so the number should be interpreted alongside other health measures.
Does this calculator tell me how to change my BMI?
No. It only calculates BMI from the weight and height you enter and shows the adult category for that number. It does not provide a diet, exercise, or weight-change plan.
Is BMI used the same way in every country?
Most countries follow the WHO adult cutoffs, but some (like several Asian nations) use lower thresholds for overweight and obesity because health risks appear at lower BMIs in those populations.