BMI Calculator
Calculate your Body Mass Index (BMI) instantly. Find out if you're underweight, normal, overweight, or obese.
Last updated: June 2026
BMI Scale
Example: 5'10" Person Weighing 180 lbs
Inputs
Results
What This Means
→ This example shows someone who is slightly above the normal BMI range. A BMI of 25.8 falls into the "overweight" category, beginning at 25.
→ This doesn't necessarily mean this person is unhealthy—it's a screening tool. Someone who is very muscular, athletic, or has a different build might be in this range while being completely healthy.
→ However, research shows that people with BMIs consistently above 25 have statistically higher risks of weight-related health conditions. The next step would be to discuss weight and health with a doctor, who can evaluate fitness level, family history, and other factors.
→ A BMI of 24.9 would fall into the normal range. For this person to reach normal weight at 5'10", they would need to weigh around 179 lbs—essentially no change needed, or this could be within the margin of daily weight fluctuation.
Our calculators are built using established financial and scientific formulas. Finance tools follow standard amortization and compound interest principles. Health tools use WHO and NIH reference standards.
Last reviewed: June 2026
Learn more about our methodology →About the BMI Calculator
What Is BMI and Why It Matters
Body Mass Index (BMI) is a simple measurement that relates your weight to your height, providing a general screening tool for weight categories. It's widely used by doctors, health organizations (including WHO), and researchers as a quick, non-invasive way to assess whether someone's weight is in a healthy range for their height.
However, BMI is just one tool and doesn't measure body fat directly. It can't distinguish between muscle and fat, so athletes may have high BMIs despite being fit. For most people, though, BMI provides helpful guidance about whether weight-related health risks may increase.
The BMI Formula and Calculation
BMI is calculated the same way worldwide using this formula:
BMI = weight (kg) / [height (m)]²
Or in imperial units:
BMI = [weight (lbs) / height (in)²] × 703
Our calculator automatically converts between metric and imperial units, so you can enter your measurements however is most comfortable.
BMI Categories According to WHO Standards
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5–24.9 (target for most people)
- Overweight: BMI 25–29.9
- Obese Class I: BMI 30–34.9
- Obese Class II: BMI 35–39.9
- Obese Class III: BMI ≥ 40
These categories are based on research showing increased health risks associated with lower and higher BMIs. A BMI in the "normal" range correlates with lower risk of weight-related diseases.
What Your BMI Results Mean
Your BMI result helps you understand whether you're at increased health risk due to weight. Higher BMI correlates with increased risk of type 2 diabetes, heart disease, high blood pressure, and certain cancers. However, context matters: an athlete with high muscle mass, someone with exceptional fitness but genetic predisposition to higher weight, or someone with medical conditions should discuss their personal BMI with a doctor.
Important Limitations of BMI
BMI doesn't account for:
- Muscle mass — Muscle weighs more than fat, so very muscular people may have high BMIs despite being fit
- Bone density — Denser bones naturally add weight
- Age and metabolism — Healthy ranges may shift with age
- Individual genetics — Some people are naturally built differently
For a complete health assessment, discuss your weight with a doctor. They can evaluate BMI along with fitness level, family history, and other health markers.
Age Considerations
BMI categories are designed for adults (18+). Children and teens have different BMI standards because body composition changes with age and varies by sex. If calculating BMI for someone under 18, consult a pediatrician for proper interpretation.
Body Composition Beyond BMI
If you want a more detailed picture, consider:
- Waist circumference — Abdominal fat carries more health risks
- Body fat percentage — Measures fat directly (requires testing)
- Fitness level — Cardio, strength, and flexibility matter
- Lab work — Blood pressure, cholesterol, blood sugar
Frequently Asked Questions
BMI is a useful screening tool but not a complete health measure. It's good at identifying population-level trends but less accurate for individuals. It can't distinguish muscle from fat, doesn't account for bone density, and misses important markers like fitness level, blood pressure, and cholesterol. Use BMI as one data point, not the only measure of health.
How to Use This Calculator
- 1Enter your height in feet and inches, or in centimeters if you prefer metric units.
- 2Enter your current weight in pounds, kilograms, or stones.
- 3Enter your age. While BMI is primarily for adults, enter your age for reference.
- 4Click "Calculate BMI" to see your results.
- 5Check your category—underweight, normal weight, overweight, or obese.
- 6Remember that BMI is a screening tool. Combine this result with other health markers and discuss with your doctor for a complete picture.