BMI Calculator
Calculate your Body Mass Index instantly and see which weight category you fall into, for metric or imperial units.
BMI Calculator — input your values
Learn more
Did you know?
BMI estimates body weight based on height and weight — it does not directly measure body fat.
WHO recommendation
Healthy BMI for most adults is between 18.5 and 24.9.
Important
Athletes may have a higher BMI because of increased muscle mass — BMI doesn't distinguish muscle from fat.
What does this health calculator do?
The BMI (Body Mass Index) calculator is designed for adults and computes a simple ratio of your weight to your height: BMI = weight (kg) ÷ height² (m). It's one of the most widely used health screening tools and works with both metric and imperial units, so you can calculate your BMI with height and weight in kg and cm or pounds and inches.
Your result is compared against the standard adult BMI ranges — the BMI chart — to place you in a weight category: underweight, healthy weight, overweight or obese. The calculator also shows the healthy weight range for your height.
Formula and variables
For imperial measurements: BMI = 703 × weight (lb) / height² (in²).
| Symbol | Meaning |
|---|---|
| weight | Body mass in kilograms |
| height | Height in meters (centimeters ÷ 100) |
Worked example
A 30-year-old person weighs 75 kg and is 175 cm tall.
- Height: 175 cm = 1.75 m.
- Square the height: 1.75² = 3.0625 m².
- BMI = 75 ÷ 3.0625 = 24.49.
Answer: BMI ≈ 24.5 — healthy weight.
Tips and common mistakes
Tips
- BMI is most useful as a population screening tool — combine it with waist circumference for a fuller picture.
- For children and teens, BMI is interpreted using age- and sex-specific percentile charts, not adult ranges.
- Weight changes slowly — measure at the same time of day for consistency.
- Track BMI alongside body fat percentage and lifestyle habits rather than chasing a number alone.
Common mistakes to avoid
- Using the adult BMI ranges for children or teenagers under 20.
- Interpreting BMI as a direct measure of body fat — athletes often score high despite low body fat.
- Forgetting to convert centimeters to meters before using the metric formula.
BMI Calculator — frequently asked questions
What is a good BMI?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight. Below 18.5 is underweight and 25 or above is overweight or obese.
How is BMI calculated?
Metric: divide weight in kilograms by height in meters squared. Imperial: multiply weight in pounds by 703, then divide by height in inches squared.
Is BMI accurate for athletes?
Not always — BMI doesn't distinguish muscle from fat. A muscular athlete can have a high BMI with very low body fat. Body fat percentage or waist-to-height ratio can be more informative.
Is BMI different for men and women?
The adult BMI categories are the same for both sexes, though healthy body fat percentages differ. Some research suggests slightly different optimal ranges, but the standard categories remain the norm.
Can I use this BMI calculator with pounds and inches?
Yes — switch the unit selector to imperial. The calculator converts inches and pounds to meters and kilograms automatically, so you can calculate your BMI in lbs and inches without doing the conversions yourself.
Is BMI reliable for older adults?
BMI can be less meaningful in older age due to height loss and changing body composition. Waist circumference is often a better indicator of risk in older adults.
What should I do if my BMI is high?
Talk to a healthcare professional. Sustainable changes — balanced nutrition, regular activity and adequate sleep — are more effective than crash diets.
How this calculator works
BMI is computed as weight in kilograms divided by the square of height in meters. The result is compared against the standard adult weight categories from the World Health Organization.
Limitations
- Does not distinguish muscle from fat, so it can misclassify athletes and very muscular individuals.
- Not designed for children under ~20, pregnant women, or older adults with significant height loss.
- BMI alone is not a diagnosis — it should be combined with other health indicators.
Sources and references
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