BMI Calculator
Calculate Body Mass Index from height and weight.
Input & results
Input values
Results
Enter values to see instant results.
Calculation History
- Your calculations will appear here.
Recent calculations are saved automatically as you adjust inputs.
Health and fitness results are estimates for general informational purposes only and are not medical advice. Consult a qualified healthcare professional before making health decisions. See our full disclaimer.
What is BMI?
A BMI (Body Mass Index) Calculator is a quick screening tool that classifies your weight relative to your height into categories such as underweight, normal, overweight, or obese.
BMI is calculated by dividing weight in kilograms by height in meters squared. It is a widely used, inexpensive screening measure that helps identify potential weight-related health risks at a population level. While BMI does not directly measure body fat or distinguish muscle from fat, it remains a useful first indicator used by clinicians and fitness professionals worldwide.
Why is it used?
BMI gives a fast, standardized snapshot of whether your weight falls in a healthy range for your height. It is helpful for tracking progress during a fitness program and for starting a conversation about health risks with a professional.
Who should use it?
Adults monitoring their general health or fitness progress. It is not intended for children, pregnant women, or competitive athletes without additional assessment.
How it works
- Enter your weight in kilograms and height in centimeters.
- The calculator converts height to meters and applies BMI = weight ÷ height².
- Your BMI value is mapped to a standard category (underweight through obese).
- Results update instantly as you change inputs.
Formula
Variable definitions
| Variable | Meaning |
|---|---|
| weight | Body weight in kilograms |
| height | Height in meters |
| BMI | Body Mass Index (kg/m²) |
How the formula works
- Convert height to meters (e.g. 170 cm = 1.70 m).
- Square the height in meters.
- Divide weight in kilograms by the squared height.
- Compare the result to standard BMI categories.
Example calculation
BMI for a person weighing 70 kg at 170 cm tall.
| Input | Value |
|---|---|
| Weight | 70 kg |
| Height | 170 cm |
- Height = 1.70 m
- 1.70² = 2.89
- BMI = 70 ÷ 2.89
- BMI ≈ 24.2
Result
More examples
85 kg at 170 cm.
| Input | Value |
|---|---|
| Weight | 85 kg |
| Height | 170 cm |
- BMI = 85 ÷ 2.89 = 29.4
Result
Methodology
- Gather Weight (kg), Height (cm) from your documents or estimates.
- Enter each value in the matching field; units must match the labels.
- The calculator applies the BMI formula and updates results in real time.
- Compare scenarios by changing one input at a time.
Benefits
- Quick health screening with no special equipment.
- Track changes during a weight-management program.
- Understand where you fall on the WHO BMI scale.
- Start an informed conversation with a clinician.
Use cases
- Setting a fitness baseline before training.
- Routine health checkups and wellness programs.
- Educational context for nutrition planning.
- Monitoring trends over time.
Tips & important notes
- BMI may misclassify muscular athletes as overweight.
- Pair BMI with waist measurement for a fuller picture.
- Children and teens use age- and sex-specific percentiles.
- Use it as a screening tool, not a diagnosis.
Common mistakes
- Entering height in centimeters without converting to meters.
- Treating BMI as a direct measure of body fat.
- Applying adult categories to children or athletes.
Related concepts
- Body fat percentage and composition
- Waist-to-height ratio
- BMR and daily calorie needs
Good to know