ToolNix.io
BMI Calculator
Calculate your Body Mass Index and find out what it means for your health.
Your Measurements
🇺🇸 Imperial (lbs / ft)
🌍 Metric (kg / cm)
Your Results
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UnderweightNormalOverweightObese
BMI Categories
⚖️ About This Calculator
Our free BMI Calculator instantly computes your Body Mass Index using either imperial (lbs, ft/in) or metric (kg, cm) measurements. BMI is a widely used screening tool recommended by the WHO and NHS to assess whether a person has a healthy body weight relative to their height.
Along with your BMI score and category, our calculator shows your healthy weight range and personalized health guidance — giving you actionable insights, not just a number.
📋 How to Use the BMI Calculator
1
Select your unit system — Choose between Imperial (lbs, feet/inches) used in USA, or Metric (kg, cm) used in UK, Canada and most countries.
2
Enter your weight — Input your current body weight in pounds or kilograms.
3
Enter your height — Input your height in feet and inches, or in centimeters.
4
Click Calculate BMI — Your BMI score appears instantly along with your weight category.
5
Review your results — See your BMI value, category (Underweight/Normal/Overweight/Obese), healthy weight range for your height, and personalized health recommendations.
❓ Frequently Asked Questions
According to WHO guidelines, a BMI between 18.5 and 24.9 is considered healthy for most adults. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is classified as obese. These ranges apply equally to men and women, though body composition can vary significantly between individuals.
BMI is less accurate for athletes because it does not distinguish between fat mass and muscle mass. A highly muscular person may have a high BMI but very low body fat percentage. For athletes, body fat percentage measurement through DEXA scan or skinfold calipers is more meaningful than BMI alone.
For metric units: BMI = weight (kg) divided by height (m) squared. Example: 70kg and 1.75m gives BMI = 70 / (1.75 x 1.75) = 22.9. For imperial units: BMI = (weight in pounds x 703) divided by (height in inches squared). Our calculator handles both unit systems automatically.
Yes, BMI is interpreted differently for children and teenagers aged 2 to 19. Instead of fixed ranges, pediatric BMI uses age-specific and sex-specific percentile charts. Our calculator is designed for adults aged 18 and over. For children, please consult a pediatrician for accurate assessment.
Yes, this is known as normal weight obesity or being skinny fat. A person can have a normal BMI but carry excess body fat around vital organs (visceral fat), which increases health risks. Waist circumference, waist-to-hip ratio, and body fat percentage provide additional health insights beyond BMI alone.