Introduction
The BMI Calculator estimates adult Body Mass Index using height and weight. BMI is a quick screening number that can help identify whether a person falls into an underweight, normal, overweight, or obesity category, but it should be interpreted with context because it does not directly measure body fat, muscle mass, or overall health.
How to Use
Choose metric or imperial units, then enter your height and weight. The calculator updates your BMI result and category automatically. For the most useful result, measure height without shoes and use a recent weight measurement. Treat the output as a screening guide, not as a diagnosis.
Features
- •Supports metric units (kg/cm) and imperial units (lb/ft/in)
- •Instant BMI result with adult weight category
- •Clear BMI category table for quick interpretation
- •Practical notes about BMI limitations and measurement accuracy
- •Useful for wellness tracking, fitness planning, and general screening
- •Free browser tool with no account required
What BMI Can and Cannot Tell You
BMI is popular because it is simple: it compares body weight with height using a standard formula. It can be useful for population-level screening and for noticing broad changes over time. However, BMI does not show body composition. A muscular athlete and a sedentary person can have the same BMI but very different health profiles.
How to Interpret Your BMI Responsibly
Use BMI as a starting point. If your result is outside the normal adult range, consider it a signal to look more closely at lifestyle, waist measurement, blood pressure, lab results, family history, and professional medical advice. Do not use BMI alone to make medical decisions.
Measurement Tips
- Measure height standing straight, without shoes.
- Use a consistent scale and weigh at a similar time of day when tracking trends.
- Recheck unusual results to avoid unit or typing mistakes.
- For children, teens, pregnant people, older adults, and highly muscular athletes, BMI needs extra context.
Adult BMI Category Reference
Common adult BMI categories used for general screening. BMI is measured in kg/m2.
| Classification | BMI Range |
|---|---|
| Severe thinness | Below 16 |
| Moderate thinness | 16.0 - 16.9 |
| Mild thinness | 17.0 - 18.4 |
| Normal range | 18.5 - 24.9 |
| Overweight | 25.0 - 29.9 |
| Obesity class I | 30.0 - 34.9 |
| Obesity class II | 35.0 - 39.9 |
| Obesity class III | 40.0 and above |
When BMI Needs Extra Context
BMI is a screening tool. These situations often require a more complete health assessment.
| Situation | Why BMI May Be Limited |
|---|---|
| Athletes or strength training | Higher muscle mass can raise BMI without indicating excess body fat |
| Children and teens | BMI is interpreted by age and sex percentiles |
| Pregnancy | Weight changes are expected and need pregnancy-specific guidance |
| Older adults | Muscle loss and body composition changes can affect interpretation |
Frequently Asked Questions
What is BMI?
BMI stands for Body Mass Index. It is calculated from weight and height and used as a general screening measure for adult weight categories.
What is the BMI formula?
In metric units, BMI = weight in kilograms / height in meters squared. In imperial units, BMI = 703 x weight in pounds / height in inches squared.
What is a healthy BMI range for adults?
For most adults, the normal BMI range is commonly listed as 18.5 to 24.9. Individual health can still vary, so BMI should be interpreted with other health information.
Is BMI accurate for everyone?
No. BMI is useful for broad screening but does not directly measure body fat or account for muscle mass, age, pregnancy, or body composition.
Can children use this BMI calculator?
This calculator is intended for adults. Children and teens need BMI percentile charts based on age and sex.