BMI Calculator
Calculate your Body Mass Index using either metric or imperial units.
What Is Body Mass Index (BMI)?
Body Mass Index (BMI) is a quick screening tool that compares your weight to your height. It is widely used by doctors, fitness professionals, and public health researchers to estimate whether someone falls into a healthy weight range.
BMI does not directly measure body fat, but it can still provide a useful starting point for understanding your overall health status. Think of it as a first signal, not a final diagnosis.
How to Use This BMI Calculator
- Select your preferred unit system: metric or imperial.
- Enter your weight and height.
- Click Calculate BMI.
- Review your BMI score, category, and healthy weight range estimate.
For best accuracy, measure your height without shoes and use your most current body weight.
BMI Categories for Adults
| BMI Range | Weight Status |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Normal / Healthy Weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity Class I |
| 35.0 to 39.9 | Obesity Class II |
| 40.0 and above | Obesity Class III |
How BMI Is Calculated
Metric Formula
BMI = weight (kg) / [height (m)]²
Imperial Formula
BMI = 703 × weight (lb) / [height (in)]²
This calculator handles both formulas for you automatically and rounds the result to one decimal place.
What Your BMI Result Means
If Your BMI Is Under 18.5
You may be underweight. In some cases, this can be related to inadequate nutrition, illness, high metabolism, or other factors. A healthcare professional can help you identify the cause and create a balanced plan.
If Your BMI Is Between 18.5 and 24.9
This is generally considered a healthy range for many adults. Continue focusing on regular movement, quality sleep, stress management, and nutrient-dense foods to maintain overall wellness.
If Your BMI Is 25 or Higher
You may be in the overweight or obesity range. This may increase risk for conditions such as high blood pressure, type 2 diabetes, and heart disease. Even modest lifestyle improvements can make a meaningful difference over time.
Important Limitations of BMI
BMI is useful, but it has limits. It does not account for:
- Muscle mass vs. fat mass
- Fat distribution (for example, abdominal fat)
- Age-related body composition changes
- Differences by ethnicity and body type
- Pregnancy or specific medical conditions
For a fuller picture, combine BMI with waist measurement, blood markers, fitness level, and medical guidance.
Healthy Ways to Improve Your BMI
- Build meals around lean protein, vegetables, whole grains, and healthy fats.
- Reduce ultra-processed foods and sugary drinks.
- Aim for at least 150 minutes of moderate activity weekly.
- Include strength training 2 to 3 times per week.
- Sleep 7 to 9 hours per night and manage chronic stress.
- Track progress monthly, not daily, to focus on long-term trends.
Frequently Asked Questions
Is BMI accurate for athletes?
Not always. Athletes with high muscle mass may have a high BMI but low body fat. In those cases, additional assessments are better indicators.
Can children use this BMI calculator?
Children and teens require age- and sex-specific BMI percentiles, so this calculator is intended for adults.
How often should I check BMI?
Once every few weeks or monthly is usually enough to monitor trends without over-focusing on short-term fluctuations.
Use this BMI calculator as a practical starting point. If your result concerns you, consider speaking with a qualified healthcare provider for personalized guidance.