BMI Calculator — Healthy Weight Chart
Calculate your Body Mass Index (BMI) using height and weight. Supports both metric and imperial units. Includes BMI chart and health classification.
Your BMI
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BMI Categories (WHO)
Underweight < 18.5
Normal weight 18.5 – 24.9
Overweight 25.0 – 29.9
Obese Class I 30.0 – 34.9
Obese Class II 35.0 – 39.9
Obese Class III ≥ 40.0
BMI Formula
BMI = weight (kg) / height² (m) Imperial: BMI = 703 × weight (lb) / height² (in)
Frequently Asked Questions
- BMI = weight (kg) ÷ height² (m²). Example: 70 kg ÷ (1.75m × 1.75m) = 22.9. In imperial units: BMI = 703 × weight (lbs) ÷ height² (inches²). A BMI of 18.5–24.9 is considered normal weight.
- The BMI formula is the same for men and women. However, the interpretation differs slightly — women naturally carry more body fat than men at the same BMI. Some health professionals use adjusted ranges: a BMI of 21–23 is considered optimal for women; 22–24 for men. Athletes may also have elevated BMI due to muscle mass.
- According to the WHO: Under 18.5 = Underweight; 18.5–24.9 = Normal weight; 25.0–29.9 = Overweight; 30.0+ = Obese. The ideal BMI range for most adults is 20–25. For adults over 65, a slightly higher BMI (25–27) may be protective.
- No — BMI is not accurate for people with high muscle mass. Muscle weighs more than fat, so athletes often have a 'overweight' or 'obese' BMI despite having low body fat. Better measures for athletes include body fat percentage, waist-to-hip ratio, or DEXA scans.
- The most common methods: Skinfold calipers (measures skin folds at multiple sites); Bioelectrical impedance (sends a small current through the body); Navy method (uses neck and waist measurements); DEXA scan (most accurate, medical-grade). Healthy body fat: men 10–20%, women 18–28%.
- A BMI of 30 or above is classified as obese. Obesity is further categorized: Class I (30–34.9), Class II (35–39.9), and Class III or 'severe obesity' (40+). Obesity is associated with increased risk of type 2 diabetes, heart disease, high blood pressure, and certain cancers.
- BMI uses the same formula for all adults, but interpretation changes with age. For children and teens, BMI is age- and sex-specific (called BMI-for-age percentile). For older adults (65+), a BMI of 25–27 may actually be associated with better health outcomes than a 'normal' BMI.
- To reduce BMI, you need to lose body fat through a combination of: caloric deficit (eating fewer calories than you burn), regular aerobic exercise (150+ minutes/week), and strength training (builds muscle, increases metabolism). A safe rate of weight loss is 0.5–1 kg (1–2 lbs) per week.
- BMI does not account for: muscle vs. fat distribution, bone density, age, sex, or ethnicity. It also doesn't measure where fat is stored — visceral fat (around organs) is more dangerous than subcutaneous fat. BMI is a useful population-level screening tool but should be combined with other assessments for individual health evaluation.