Body Mass Index Calculator
Quickly estimate your BMI using metric or imperial units. This tool is for educational use and does not replace professional medical advice.
What is a body mass index calcul?
A body mass index calcul (BMI calculation) is a simple way to estimate whether your body weight is low, moderate, or high compared with your height. It is widely used in public health and primary care because it is fast, inexpensive, and easy to repeat over time.
BMI is not a direct measurement of body fat, but it is often useful as a first screening tool. If your BMI is outside the normal range, it can be a signal to look deeper at nutrition, physical activity, sleep, stress, and possible medical conditions.
BMI formula
Metric formula
BMI = weight (kg) ÷ [height (m)]²
Example: 70 kg and 1.75 m gives BMI = 70 ÷ (1.75 × 1.75) = 22.9.
Imperial formula
BMI = 703 × weight (lb) ÷ [height (in)]²
Example: 154 lb and 69 in gives BMI = 703 × 154 ÷ (69 × 69) = 22.7.
Adult BMI categories
- Below 18.5: Underweight
- 18.5 to 24.9: Normal weight
- 25.0 to 29.9: Overweight
- 30.0 and above: Obesity
These cutoffs are commonly used for adults. For children and teens, BMI is interpreted differently using age- and sex-specific percentiles.
How to use this calculator
- Select your preferred unit system (metric or imperial).
- Enter your current weight and height accurately.
- Click Calculate BMI.
- Read your BMI score, category, and estimated healthy weight range.
Why BMI is useful
Used responsibly, BMI can be a practical tool for trend tracking. A single number is less important than long-term direction. If your BMI steadily rises over months, that trend may indicate an energy imbalance, reduced activity, stress-related eating, or other health factors worth addressing.
BMI is also useful at the population level. Health organizations use it to monitor obesity prevalence and to design nutrition and movement programs for communities.
Limitations of BMI
BMI has limits, and context matters. Two people can have the same BMI but very different health profiles.
- Muscular individuals: Athletes may have a high BMI despite low body fat.
- Body fat distribution: BMI does not show where fat is stored (for example, abdominal fat).
- Age and sex factors: Body composition changes across the lifespan.
- Ethnic variation: Some populations face metabolic risk at lower BMI ranges.
For a fuller picture, combine BMI with waist circumference, blood pressure, blood glucose, lipid markers, fitness level, and medical history.
Healthy ways to improve BMI over time
If your BMI is above normal
- Focus on sustainable calorie balance, not crash dieting.
- Prioritize high-fiber foods, lean proteins, and minimally processed meals.
- Aim for 150+ minutes of weekly moderate activity plus strength training.
- Improve sleep quality and manage stress to support appetite regulation.
If your BMI is below normal
- Increase calories gradually with nutrient-dense foods.
- Add resistance training to support muscle gain.
- Eat balanced meals consistently through the day.
- Talk with a healthcare professional if unintentional weight loss occurs.
Final note
A body mass index calcul is best treated as a starting point, not a final judgment. Use it to guide questions, track changes, and support better health decisions. If your result concerns you, consult a clinician or registered dietitian for a personalized plan.