BMI Calculator
Calculate your Body Mass Index (BMI) using metric or imperial units. Understand your BMI category and what it means for general health.
This calculator is for general adult BMI screening only. It is not a diagnosis and does not replace advice from a qualified healthcare professional.
How it works
How BMI Is Calculated
BMI (Body Mass Index) is calculated by dividing weight by height squared. It is widely used as a simple screening tool to classify weight status in adults.
Metric formula: BMI = weight (kg) ÷ height (m)²
Imperial formula: BMI = (weight (lb) ÷ height (in)²) × 703
How to interpret results:
- Underweight may indicate insufficient body weight
- Normal range is generally associated with lower health risk
- Overweight and obesity are associated with increased risk of certain conditions
BMI does not measure body fat directly. It should be used together with other indicators such as waist circumference, lifestyle factors, and clinical evaluation.
What BMI Means
Body Mass Index is one of the most common screening tools used to evaluate whether an adult’s weight is generally appropriate for their height. It is simple, fast, and widely used in public health, fitness, and everyday health monitoring. Because BMI only needs height and weight, it provides an easy way to classify general weight status without requiring medical equipment.
That convenience is why BMI is commonly used in clinics, health checkups, workplace wellness programs, and personal fitness tracking. It helps people quickly understand whether they fall into a broad category such as underweight, normal weight, overweight, or obesity. These categories are not diagnoses, but they are useful starting points for understanding possible weight-related health risk.
Why BMI Is Useful
BMI is useful because it creates a standard reference point. Two people may have different body shapes, but BMI provides a simple mathematical way to compare weight relative to height. In general, very low BMI may suggest undernutrition or other health concerns, while very high BMI may be associated with increased risk for conditions such as type 2 diabetes, high blood pressure, and cardiovascular disease.
This does not mean BMI tells the whole story. Instead, it helps answer a narrow question: “Based on height and weight alone, where does this person fall on a standard adult weight scale?”
Important Limitations
BMI is not the same as body fat percentage. It cannot distinguish between fat mass and muscle mass. A muscular athlete may have a high BMI even though their body fat is relatively low. On the other hand, someone may fall into a normal BMI range while still having health risks related to fat distribution or low muscle mass.
BMI also does not measure waist circumference, metabolic health, fitness level, age-related body composition changes, or medical history. That is why BMI works best as a screening metric rather than a final judgment about health.
Real-World Use Cases
- General health check: Quickly see whether your height and weight place you in a common adult BMI category
- Weight trend tracking: Compare results over time while changing diet, exercise, or lifestyle habits
- Goal setting: Use BMI as one reference point when considering weight gain, weight loss, or maintenance
- Health education: Understand the difference between a quick screening tool and a full body composition assessment
How to Use BMI Responsibly
A BMI result should be interpreted together with other factors such as body fat percentage, waist circumference, blood test results, physical activity, and advice from a healthcare professional. If your BMI is outside the normal range, it does not automatically mean you are unhealthy. It simply means the result may be worth discussing in a broader health context.
In short, BMI is useful because it is simple and standardized. Its weakness is also that it is simple. The best way to use it is as a starting point for understanding weight status, not as the only measure of health.
Examples
- General health check: A person enters height and weight to quickly assess if they are within a normal BMI range.
- Fitness tracking: Monitor BMI changes over time when adjusting diet or exercise.
- Weight management planning: Identify whether weight loss or gain may be appropriate.
Example calculations:
- 170 cm, 65 kg → BMI = 65 ÷ (1.70²) = 22.49 (Normal)
- 180 cm, 90 kg → BMI = 90 ÷ (1.80²) = 27.78 (Overweight)
- 70 in, 160 lb → BMI = (160 ÷ 70²) × 703 = 22.96 (Normal)
FAQ
- Is BMI accurate?
BMI is a screening tool based on height and weight. It does not directly measure body fat, muscle mass, or individual health risk.
- Is this BMI calculator for adults only?
Yes. The BMI categories shown here are for adults. Children and teens require age- and sex-specific BMI percentiles.
- Does BMI consider muscle?
No. Individuals with higher muscle mass may have a higher BMI without having excess body fat.
- Which BMI categories are used?
Standard adult BMI categories: underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), obesity (≥30).
- What does my BMI result mean?
Your BMI category indicates general weight status. It should be interpreted alongside other health indicators such as waist circumference, body fat percentage, and medical advice.
- Is my data stored?
No. All calculations run locally in your browser and no personal data is uploaded or stored.
- Can BMI diagnose health problems?
No. BMI is not a diagnosis. It is only a quick screening metric that may suggest whether a person should look more closely at weight-related health risks.
- Why can two people with the same BMI look different?
Because BMI only uses height and weight. It does not distinguish between muscle, fat, bone density, or body shape.