BMI Calculator
Want to check if your weight is in a healthy range? Enter your height and weight and you will see your BMI and what category you fall into. It is quick, simple, and gives you a useful starting point.
TL;DR
- You divide weight by height squared and compare the result to WHO thresholds.
- Standard Metric Formula: BMI = Weight (kg) ÷ Height (m)²
- Example 1: Metric calculation for an average adult — Weight: 70 kg, Height: 1.75 meters
How it works
You divide weight by height squared and compare the result to WHO thresholds. Below 18.5 is underweight, 18.5 to 24.9 is healthy, 25 to 29.9 is overweight, and 30 or more is obese.
The math
Use kilograms and meters. Square your height, then divide weight by that number. With pounds and inches, multiply by 703.
First, square the height in meters (multiply height by itself). Then, divide the total body mass in kilograms by that squared value to find the ratio.
WHO BMI categories
| Category | BMI range (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| Normal weight | 18.5 - 24.9 |
| Overweight | 25.0 - 29.9 |
| Obesity | ≥ 30.0 |
BMI beyond the number: table, limits & edge cases
BMI is weight ÷ height², but it reads differently for a muscular man with BMI 27 and 12% body fat vs a teenager where accurate BMI for teenagers needs percentiles. Our table: <18.5 underweight, 18.5-24.9 normal, 25-29.9 overweight, ≥30 obesity. For kids/pregnancy use dedicated curves — that’s why we also link WHO/CDC and the body-fat calculator.
| BMI | Category | Note |
|---|---|---|
| <18.5 | Underweight | WHO |
| 18.5-24.9 | Normal | Gauge 22.8 |
| 25-29.9 | Overweight | WHO |
| ≥30 | Obesity | CDC/NHLBI |
Source: WHO Obesity, CDC BMI, NHLBI.
Examples
Example 1: Metric calculation for an average adult
- Weight: 70 kg, Height: 1.75 meters
- Calculate squared height: 1.75 × 1.75 = 3.0625 m²
- Divide weight by squared height: 70 ÷ 3.0625 = 22.86
- Result: BMI of 22.9, which is in the optimal 'Healthy Weight' range.
Example 2: Imperial units calculation
- Weight: 154 lbs, Height: 5 feet 10 inches (70 inches total)
- Square the height in inches: 70 × 70 = 4,900 in²
- Divide weight by height squared: 154 ÷ 4,900 = 0.0314
- Multiply by conversion factor: 0.0314 × 703 = 22.09
- Result: BMI of 22.1, indicating a perfectly normal weight status.
When to use it
✦ Personal Fitness and Health Baselines
Use your BMI as a starting metric when initiating a weight management or cardiovascular health plan.
✦ Medical and Clinical Screenings
Doctors use BMI during routine checkups to assess general cardiovascular risks before running more expensive body composition tests.
✦ Insurance and Public Health Research
Epidemiologists study regional BMI statistics to design public health nutrition and exercise programs.
⚠ Common mistakes
- The Athlete Fallacy: BMI does not distinguish between muscle tissue and fat mass. Bodybuilders or professional athletes often have high BMIs classified as 'overweight' due to high muscle density.
- Ignoring Frame Size and Bone Density: It assumes standard skeletal dimensions and does not account for natural body frame variances.
FAQ (4)
Is BMI accurate for children and teenagers?
No, children's bodies are still growing. For children, pediatricians use BMI-for-age percentiles rather than adult thresholds.
Does BMI measure direct body fat percentage?
No, it estimates weight categories but cannot measure actual body fat or lean body tissue.
Why is my BMI overweight if I am muscular?
BMI cannot tell fat from muscle: a lifter at BMI 27 with 12% body fat is classified overweight though lean. Check waist circumference and body-fat percentage alongside — for athletes those matter more than BMI.
Can BMI be too low?
Yes: below 18.5 is underweight and can signal under-eating, illness or overtraining. If low with fatigue, hair loss or missed cycles, see a doctor and a dietitian rather than just eating more.
Sources & References
⚠ Health Disclaimer
This tool provides estimates for informational purposes only and does not constitute medical, veterinary, or professional advice. Always consult a qualified healthcare professional before making decisions about your health or treatment.