What Your BMI Number Really Tells You
Body Mass Index (BMI) is the most widely used screening tool for weight categories. While it's not perfect, it gives you and your healthcare provider a quick snapshot of potential health risks related to your weight.
Use our BMI Calculator to find your number in seconds.
The BMI Formula
Metric: BMI = Weight (kg) ÷ Height² (m²)
Imperial: BMI = (Weight in lbs ÷ Height² in inches) × 703
Example Calculation
A person who weighs 70 kg and is 1.70 m tall:
70 ÷ (1.70 × 1.70) = 70 ÷ 2.89 = BMI 24.2 → Normal Weight
BMI Categories Explained
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Malnutrition, weak immunity |
| 18.5 - 24.9 | Normal | Lowest health risk |
| 25.0 - 29.9 | Overweight | Moderate risk |
| 30.0 - 34.9 | Obese Class I | High risk |
| 35.0 - 39.9 | Obese Class II | Very high risk |
| 40+ | Obese Class III | Extremely high risk |
When BMI Gets It Wrong
BMI isn't perfect. Here are situations where it may be misleading:
Athletes and Bodybuilders
Muscle weighs more than fat. A muscular athlete may have a BMI of 28 (Overweight) but very low body fat. That's why our BMI Calculator also estimates body fat percentage when you provide age and gender.
Older Adults
Seniors naturally lose muscle mass, which can give them a "normal" BMI while having high body fat.
Different Ethnic Groups
- South Asians: Higher health risk at lower BMI (overweight considered at 23+)
- African Americans: May have lower body fat at same BMI
Pregnant Women
BMI is not applicable during pregnancy. Use pre-pregnancy weight instead.
Beyond BMI — Other Health Metrics to Track
For a complete picture of your health:
Waist Circumference: Belly fat is more dangerous than hip fat
- Men: Should be below 40 inches (102 cm)
- Women: Should be below 35 inches (88 cm)
Waist-to-Hip Ratio: Measures fat distribution
- Healthy: Below 0.9 for men, below 0.85 for women
Body Fat Percentage: More accurate than BMI
- Men: 10-20% is healthy
- Women: 18-28% is healthy
How to Reach and Maintain a Healthy BMI
If You're Underweight
- Eat calorie-dense nutritious foods (nuts, avocado, whole grains)
- Eat 5-6 smaller meals throughout the day
- Include protein with every meal
- Consider strength training to build muscle
If You're Overweight
- Create a calorie deficit (500 calories/day = ~0.5 kg/week loss)
- Prioritize protein and vegetables at every meal
- Walk 30+ minutes daily
- Drink water before meals
- Get 7-8 hours of sleep (poor sleep increases hunger hormones)
If You're in Normal Range
- Maintain your current habits
- Continue regular exercise (150 min/week)
- Monitor your weight monthly
- Get annual health check-ups
Your BMI is just one number. Use it as a starting point, not a final verdict.