Free BMI Calculator - Calculate Your Body Mass Index
Calculate your Body Mass Index (BMI) to check if you're at a healthy weight for your height. BMI is a screening tool that estimates body fat based on weight and height. Enter your measurements below for instant results.
Understanding BMI (Body Mass Index)
BMI is calculated using the formula: weight (kg) ÷ height² (m²). It's a screening tool used by healthcare providers to assess if someone might have health risks associated with body weight. However, BMI doesn't directly measure body fat percentage and doesn't account for muscle mass, bone density, or body composition.
BMI Categories (WHO Standards)
- Underweight: BMI less than 18.5 - May indicate malnutrition or health issues
- Normal weight: BMI 18.5 to 24.9 - Generally considered healthy weight range
- Overweight: BMI 25 to 29.9 - May increase health risks
- Obese Class I: BMI 30 to 34.9 - Increased health risks
- Obese Class II: BMI 35 to 39.9 - High health risks
- Obese Class III: BMI 40 or greater - Very high health risks
BMI Limitations & Considerations
Important: BMI is a screening tool, not a diagnostic tool. It has limitations:
- Doesn't distinguish between muscle and fat mass
- Athletes may have high BMI due to muscle, not fat
- Doesn't account for age, sex, or ethnicity differences
- May not be accurate for pregnant women, children, or elderly
- Doesn't measure body fat distribution
Recommendation: Use BMI as one indicator among many. Consult healthcare professionals for comprehensive health assessments including body composition analysis, waist circumference, and other health markers.
BMI Calculator Tips
- Measure weight in the morning for consistency
- Use the same scale for accurate tracking
- Measure height without shoes
- Track BMI changes over time, not single readings
- Consider waist circumference alongside BMI
BMI Calculator FAQ
Is BMI accurate for everyone?
No. BMI is less accurate for athletes (who have high muscle mass), elderly people (who may have lost muscle), pregnant women, and growing children. It's a general screening tool, not a definitive measure of health.
What's a healthy BMI?
According to WHO standards, a BMI between 18.5 and 24.9 is generally considered healthy for adults. However, ideal BMI can vary based on age, ethnicity, and individual health factors.
Can I use pounds and inches?
This calculator uses metric units (kg and cm). To convert: 1 pound = 0.45 kg, 1 inch = 2.54 cm. You can convert your measurements before entering them.
How often should I check my BMI?
For weight management, checking BMI monthly is sufficient since significant changes take time. More frequent checks aren't necessary unless recommended by healthcare providers.
Disclaimer: This BMI calculator provides estimates for informational purposes only. Results follow WHO standards but don't account for individual factors like muscle mass, bone density, or body composition. BMI is a screening tool, not a diagnostic tool. For medical advice, health assessments, or personalized guidance, consult qualified healthcare professionals. Last updated: February 2026.