Free BMI Calculator - Calculate Body Mass Index
Calculate your BMI (Body Mass Index) instantly. Free online BMI calculator with metric and imperial units to check your healthy weight range.
BMI Formula
Metric: BMI = weight(kg) / [height(m)]²
Imperial: BMI = [weight(lbs) / height(in)²] × 703
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Free BMI Calculator - Calculate Your Body Mass Index & Health Category
Calculate your BMI (Body Mass Index) instantly and discover your health category: underweight, normal weight, overweight, or obese. Get personalized insights, ideal weight ranges, and health recommendations based on WHO and CDC guidelines. Supports both metric (kg/cm) and imperial (lbs/inches) units for all ages and genders.
Quick How-To Guide
- 1Select your preferred unit system (metric or imperial)
- 2Enter your current weight in kilograms or pounds
- 3Enter your height in centimeters or feet and inches
- 4Click "Calculate BMI" to see your Body Mass Index
- 5Review your health category and recommended weight range
Why use our tool?
Instant BMI calculation—enter height and weight to get results in seconds
Health category classification—underweight, normal, overweight, or obese per WHO standards
Ideal weight range—see your healthy weight range based on your height
Visual indicators—color-coded results and BMI chart for easy understanding
Metric & imperial units—supports kg/cm and lbs/feet-inches
Age & gender considerations—different standards for adults, children, and elderly
Frequently Asked Questions
Find answers to common questions about using our tool, its features, and how it handles your data privacy.
BMI categories per WHO standards: Underweight (BMI <18.5) may indicate malnutrition or health issues; Normal weight (18.5-24.9) is associated with lowest health risks; Overweight (25-29.9) increases risk of diabetes, heart disease; Obese Class I (30-34.9), Class II (35-39.9), and Class III (40+) progressively increase risk of serious health conditions including heart disease, stroke, diabetes, and some cancers. However, BMI doesn't account for muscle mass, bone density, or body composition.
No, BMI has significant limitations for athletes and people with high muscle mass. Muscle weighs more than fat, so bodybuilders, athletes, and very active individuals may have "overweight" or "obese" BMI while actually being very healthy. For example, many NFL players have BMIs over 30 despite low body fat. For a more accurate assessment, consider body fat percentage, waist circumference, or waist-to-hip ratio alongside BMI.
For general health monitoring, checking BMI every 3-6 months is sufficient unless you're actively trying to lose or gain weight. If you're on a weight loss/gain program, monthly checks help track progress. However, don't obsess over small fluctuations—weight naturally varies by 1-2 kg day-to-day due to water retention, food intake, etc. Focus on trends over weeks, not daily changes. Combine BMI tracking with other metrics like how your clothes fit, energy levels, and overall fitness.
The BMI formula is the same for both genders, but health implications can differ. Women naturally have higher body fat percentages than men (women: 20-25% healthy, men: 10-20% healthy), so the same BMI may represent different body compositions. Some research suggests women can tolerate slightly higher BMIs without health risks. Additionally, BMI doesn't account for pregnancy or breastfeeding, where temporary weight gain is normal and healthy.
BMI is just one health indicator, not a diagnosis. If your BMI is slightly elevated but you exercise regularly, eat well, have good blood pressure/cholesterol, and feel energetic, you may be perfectly healthy. "Metabolically healthy obesity" exists—some people with higher BMIs have no metabolic abnormalities. However, don't ignore it completely. Consult a healthcare provider who can assess your overall health through blood tests, fitness tests, and body composition analysis alongside BMI.
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