BMI Calculator
Enter your height and weight to calculate your Body Mass Index (BMI). Find out your weight category based on WHO international standards.
What is BMI?
BMI (Body Mass Index) is an internationally recognized screening tool that estimates body fat based on the relationship between height and weight. Developed by Belgian mathematician Adolphe Quetelet in 1832, it is used by the World Health Organization (WHO), the CDC, and healthcare professionals worldwide as a quick assessment of weight-related health risks.
BMI Calculation Formula
Metric: BMI = weight (kg) / height (m)^2. For example, a person 175 cm tall weighing 75 kg: BMI = 75 / (1.75 x 1.75) = 75 / 3.0625 = 24.49.
Imperial: BMI = (weight in lbs x 703) / (height in inches)^2. For example, 165 lbs and 5'9" (69 in): BMI = (165 x 703) / (69 x 69) = 24.36.
BMI Categories (WHO Standard)
- Below 18.5: Underweight
- 18.5 - 24.9: Normal weight
- 25.0 - 29.9: Overweight
- 30.0 - 34.9: Obese (Class I)
- 35.0 - 39.9: Obese (Class II)
- 40.0 and above: Severe Obesity (Class III)
Average BMI by Age Group in the US (CDC/NHANES)
- Ages 20-29: Men ~26.5 / Women ~26.8
- Ages 30-39: Men ~28.2 / Women ~28.6
- Ages 40-49: Men ~28.9 / Women ~29.0
- Ages 50-59: Men ~29.2 / Women ~29.5
- Ages 60-69: Men ~29.0 / Women ~29.6
Over 42% of US adults are classified as obese (BMI 30+), and about 9.2% have severe obesity (BMI 40+), according to recent NHANES data.
Healthy Weight Ranges by Height
- 5'0" (152 cm): 97 - 128 lbs (44 - 58 kg)
- 5'4" (163 cm): 110 - 145 lbs (50 - 66 kg)
- 5'8" (173 cm): 125 - 164 lbs (57 - 74 kg)
- 6'0" (183 cm): 140 - 184 lbs (64 - 83 kg)
- 6'4" (193 cm): 156 - 204 lbs (71 - 93 kg)
Tips for Maintaining a Healthy BMI
The CDC recommends at least 150 minutes of moderate-intensity aerobic exercise per week (e.g., brisk walking, cycling) plus muscle-strengthening activities on 2 or more days. Combine regular physical activity with a balanced diet emphasizing fruits, vegetables, whole grains, and lean proteins. Aim for gradual weight changes of 1-2 pounds per week. Crash diets often lead to muscle loss and rebound weight gain, making long-term management harder.
Important Notes
BMI is a screening tool, not a diagnostic measure. It does not distinguish between muscle mass and fat mass, nor does it account for differences in body composition related to age, sex, or ethnicity. Athletes, pregnant women, and elderly individuals should use additional metrics such as body fat percentage and waist-to-hip ratio for a more comprehensive health assessment. Always consult a healthcare provider for personalized medical advice.