Free BMI Calculator
Calculate your Body Mass Index (BMI) using your height and weight. Understand what your BMI means and how it compares to healthy reference ranges. Supports both metric and imperial units.
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Understanding Your BMI Result
BMI Below 18.5
Underweight
May indicate insufficient calorie or nutrient intake. Medical guidance is advised.
BMI 18.5 – 24.9
Healthy Weight
Associated with lower risk of many weight-related health conditions for most adults.
BMI 25 – 29.9
Overweight
Modest diet and exercise improvements can help move towards a healthier range.
BMI 30 and above
Obesity Range
Associated with increased health risks. Working with a healthcare professional is recommended.
BMI Formula Explained
Metric formula:
BMI = weight (kg) ÷ height² (m²)Imperial formula:
BMI = [weight (lbs) ÷ height² (inches²)] × 703Example calculation
A person weighing 70 kg at 170 cm: BMI = 70 ÷ (1.70 × 1.70) = 70 ÷ 2.89 = 24.2 (Healthy Weight)
Limitations of BMI
BMI is a useful population-level screening tool, but it has real limitations at the individual level:
- BMI does not distinguish between muscle and fat mass. Athletes often have a high BMI despite having low body fat.
- It does not account for fat distribution. Abdominal fat carries higher health risk than fat stored elsewhere.
- Age, sex, and ethnicity can affect what is considered a healthy BMI in practice.
- Older adults may have a healthy BMI but still have unfavourable body composition.
For a more complete picture, combine BMI with body fat percentage and ideal weight range assessments.
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Related Reading
What Your BMI Actually Tells You (And What It Doesn't) →
Understanding the real value and limitations of BMI for personal health assessment.
Frequently Asked Questions
Medical Disclaimer: BMI is a screening estimate and does not diagnose health conditions. This tool is for informational purposes only and is not a substitute for professional medical advice. Full disclaimer →