BMI Calculator
Calculate your Body Mass Index to check if you're at a healthy weight for your height.
What is BMI?
Body Mass Index (BMI) is a measure of body fat based on height and weight, developed by Adolphe Quetelet. It is the most widely used screening tool for weight categories. While useful, BMI does not directly measure body fat and may not account for muscle mass.
Accuracy ±1–2 BMI units vs. clinical body-fat assessment. BMI is best used as a population-level screening tool. It may overestimate risk in athletes with high muscle mass and underestimate risk in older adults with low muscle mass. Always interpret alongside other metrics such as waist circumference or body fat percentage.
BMI Categories (WHO)
| BMI Range | Category |
|---|---|
| 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 | Obese (Class III) |
What to do with your result
- If underweight (BMI <18.5): increase calorie intake by 300–500 kcal/day with protein-rich foods and strength training. See Calorie Needs.
- If normal (BMI 18.5–24.9): maintain your current habits. Re-check every 6–12 months or if your weight changes by more than 3 kg.
- If overweight (BMI 25–29.9): aim for a 300–500 kcal/day deficit to lose 0.25–0.5 kg per week. Use our TDEE Calculator to set your target.
- If obese (BMI ≥30): consult your doctor. Also check your Waist-to-Height Ratio and Body Fat % for a more complete picture of your health risk.
Frequently Asked Questions
How accurate is the BMI calculator?
BMI is accurate to within ±1–2 units for most non-athletic adults when height and weight are measured correctly. It correlates well with body fat in large populations but can misclassify individuals who are highly muscular or very lean. Think of it as a first-line screening tool rather than a precise diagnostic measure.
What should I do after getting my BMI result?
If your BMI is in the overweight or obese range, start by calculating your TDEE to understand your daily calorie needs, then aim for a modest deficit of 300–500 kcal/day. Combine diet changes with at least 150 minutes of moderate aerobic activity per week. If your BMI is above 35 or you have related health conditions, speak with a doctor before making major changes.
How often should I recalculate my BMI?
For people actively trying to change their weight, recalculating every 4–8 weeks is reasonable. For general health monitoring, once a year is sufficient. Weigh yourself first thing in the morning after using the bathroom to minimize daily variation from food and fluid intake.
Is BMI reliable for athletes and muscular people?
BMI is less reliable for athletes because it cannot distinguish muscle from fat. A muscular individual may have a BMI above 25 while having very low body fat. In these cases, body fat percentage (measured via DEXA, hydrostatic weighing, or the US Navy circumference method) is a much better indicator of health risk.
Does BMI work the same way for all ethnicities?
No. Research shows that people of South Asian, East Asian, and some other ethnic backgrounds face higher metabolic risk at lower BMI thresholds compared to European populations. For example, the WHO suggests using a BMI of 23 (not 25) as the overweight cutoff for Asian adults. Discuss appropriate thresholds with your doctor if relevant.
This calculator is for educational purposes only. Consult a qualified healthcare professional for medical advice.