calculators.soBMI Calculator
BMI calculator to calculate your Body Mass Index and understand what it means for your health.
BMI calculator
A BMI calculator is a practical tool that allows you to quickly and easily calculate your Body Mass Index (BMI). It's a useful indicator to assess whether your weight is appropriate for your height and to understand potential health risks associated with your weight.
Easily and quickly calculate your BMI using the BMI calculator by simply entering your height and weight. The calculator supports both metric (centimeters/kilograms) and imperial (inches/pounds) units, and will provide you with your BMI value, ideal weight range, and interpret what it means for your health.
Table of contents
- What is BMI?
- How to use the BMI calculator
- Unit system support
- BMI categories and health implications
- How to calculate BMI
- Ideal weight range
- Limitations of BMI
- When to consult a healthcare professional
- BMI and Health
- Useful links and resources
What is BMI?
Body Mass Index (BMI) is a simple calculation that uses your height and weight to work out if your weight is healthy. The BMI calculation divides an adult's weight in kilograms by their height in metres squared (kg/m²).
BMI serves multiple purposes including health screening to identify potential weight-related health risks, setting realistic fitness goals, medical assessment by healthcare professionals, and understanding weight trends in population studies.
How to use the BMI calculator
The BMI calculator is easy to use and supports both metric and imperial units. To use it, first choose your unit system between metric (cm/kg) or imperial (in/lbs). Then enter your height in the selected unit system - centimeters for metric or inches for imperial. Next, input your weight in kilograms for metric or pounds for imperial. Your BMI, health category, and ideal weight range will display automatically.
The calculator will show your BMI value, ideal weight range for your height, and interpret what it means for your health.
Unit system support
The BMI calculator supports two unit systems. For the metric system, enter height in centimeters (cm) and weight in kilograms (kg) - for example, 170 cm height and 65 kg weight. For the imperial system, enter height in inches (in) and weight in pounds (lbs) - for example, 67 in height and 150 lbs weight.
The calculator automatically converts between units and provides results in your chosen system.
BMI categories and health implications
The World Health Organization (WHO) defines the following BMI categories:
| BMI Range | Category | Health Status |
|---|---|---|
| < 18.5 | Underweight | Below healthy weight range |
| 18.5 - 24.9 | Normal Weight | Healthy weight range |
| 25.0 - 29.9 | Overweight | Above healthy weight range |
| 30.0 - 34.9 | Obesity Class I | Moderately obese |
| 35.0 - 39.9 | Obesity Class II | Severely obese |
| ≥ 40.0 | Obesity Class III | Very severely obese |
Underweight (BMI < 18.5)
Being underweight may indicate malnutrition, eating disorders, or other health conditions. Consult a healthcare professional if unintentional weight loss occurs.
Normal Weight (BMI 18.5 - 24.9)
This range is generally associated with good health. Maintain healthy lifestyle habits to stay within this range.
Overweight (BMI 25 - 29.9)
This category indicates increased risk of health problems. Consider lifestyle changes to prevent further weight gain.
Obesity Class I (BMI 30 - 34.9)
This level carries higher risk of heart disease, diabetes, and other conditions. Medical consultation is recommended for weight management.
Obesity Class II (BMI 35 - 39.9)
This category shows significantly increased health risks. Medical intervention is often necessary.
Obesity Class III (BMI ≥ 40)
This level presents severe health risks requiring medical attention. Immediate medical consultation is recommended.
How to calculate BMI
The BMI formula is simple:
BMI = weight (kg) / height (m)²
Example (Metric): If you weigh 70 kg and are 1.75 m tall:
- BMI = 70 / (1.75 × 1.75) = 70 / 3.0625 = 22.9
Example (Imperial): If you weigh 154 lbs and are 69 in tall:
- Convert to metric: 154 lbs = 69.9 kg, 69 in = 1.75 m
- BMI = 69.9 / (1.75 × 1.75) = 69.9 / 3.0625 = 22.9
Ideal weight range
The calculator also provides your ideal weight range based on the healthy BMI range (18.5-24.9) for your height. This range represents the weight that is considered healthy for someone of your height.
Limitations of BMI
While BMI is a useful screening tool, it has several limitations. Athletes with high muscle mass may have high BMI despite being healthy. BMI categories may not be appropriate for older adults, and different ethnic groups may have different healthy BMI ranges. BMI doesn't distinguish between fat and muscle mass, and different BMI charts are used for children and adolescents.
When to consult a healthcare professional
Consider consulting a healthcare professional if your BMI falls outside the normal range, you have concerns about your weight, you're experiencing unexplained weight changes, or you have other health conditions that may affect your weight.
BMI and Health
BMI is just one indicator of health. Other important factors include physical activity with regular exercise being crucial for health, balanced nutrition through diet, medical history including family history and existing conditions, and lifestyle factors such as sleep, stress, and other lifestyle choices that affect health.