BMI Calculator — Calculate Body Mass Index & Health Status
Calculate Body Mass Index using metric (kg/cm) or imperial (lb/ft-in) units. Instantly shows BMI category and health risk assessment. Browser-based.
Features
- ✓Calculate Body Mass Index (BMI) instantly
- ✓Support metric units (kilograms and centimeters)
- ✓Support imperial units (pounds and feet/inches)
- ✓Show BMI category (underweight, normal, overweight, obese)
- ✓Display health risk assessment for your BMI
- ✓Calculate ideal weight range for your height
- ✓Switch between metric and imperial units
- ✓Instant calculation as you type
- ✓Based on WHO BMI classification standards
- ✓All calculations run locally in your browser
How to Use
- 1Choose your preferred unit system (metric or imperial).
- 2Enter your weight (kg or lb).
- 3Enter your height (cm or feet/inches).
- 4View your BMI result instantly.
- 5Check your BMI category and health risk assessment.
- 6See your ideal weight range for reference.
- 7Use the BMI chart to visualize where you fall on the scale.
- 8Track BMI changes over time by saving your results.
Frequently Asked Questions
What is BMI and how is it calculated?
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BMI (Body Mass Index) is a measure of body fat based on height and weight. For metric: BMI = weight(kg) / height(m)². For imperial: BMI = 703 × weight(lb) / height(in)². A BMI of 18.5-24.9 is considered normal.
What are the BMI categories?
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Underweight: BMI < 18.5. Normal weight: BMI 18.5-24.9. Overweight: BMI 25-29.9. Obese: BMI ≥ 30. These categories are based on WHO standards and help assess health risks associated with weight.
Is BMI accurate for everyone?
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BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat, so athletes may have high BMI but low body fat. It may also be less accurate for elderly people, children, and certain ethnic groups. Consider other measures like waist circumference for a complete assessment.
What is the ideal BMI range?
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The ideal BMI range is 18.5 to 24.9. This range is associated with the lowest risk of chronic diseases. However, the 'ideal' can vary based on age, ethnicity, and individual health factors. Consult a healthcare provider for personalized advice.
How do I calculate my ideal weight?
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The calculator shows your ideal weight range based on BMI 18.5-24.9 for your height. For example, at 175 cm, ideal weight is 56.7-76.2 kg. This gives you a target range to aim for.
Is my health data sent to a server?
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No. All calculations happen entirely in your browser using JavaScript. Your weight, height, and BMI results are never transmitted over the network. The tool works offline after the page loads.
Does BMI differ for men and women?
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The BMI formula is the same for both men and women. However, body composition differs between genders — women typically have higher body fat percentages at the same BMI. The health risks associated with each BMI category also vary by gender, age, and ethnicity.
How accurate is BMI for children and teenagers?
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For children and teenagers (ages 2-19), BMI is calculated the same way but interpreted using age and sex-specific percentiles rather than fixed categories. A child's BMI is compared to others of the same age and sex. This calculator uses adult standards. For children, consult a pediatrician.
What is the difference between BMI and body fat percentage?
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BMI estimates body fat based on height and weight but doesn't measure it directly. Body fat percentage measures the actual proportion of fat tissue. Two people with the same BMI can have very different body fat percentages — an athlete may have low body fat but high BMI due to muscle mass.
How often should I check my BMI?
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BMI is best used as a periodic health screening tool — checking every 1-3 months is sufficient for most people. Rapid changes in BMI (more than 0.5-1 per month) may indicate underlying health issues. For those actively managing weight, weekly checks can help track progress while focusing on gradual, sustainable changes.
Can BMI be misleading for pregnant women?
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Yes. Standard BMI calculations and categories are not accurate during pregnancy. Weight gain is expected and healthy during pregnancy. Pregnant women should follow their healthcare provider's weight gain guidelines based on pre-pregnancy BMI. Separate pregnancy weight gain charts are available from medical organizations.
What is the relationship between BMI and life expectancy?
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Population studies show a J-shaped relationship: both very low BMI (under 18.5) and very high BMI (over 30) are associated with increased mortality risk. The lowest risk is typically in the 20-25 range. However, BMI alone doesn't determine health outcomes — other factors like fitness level, diet quality, and genetics play crucial roles.
How do I measure height correctly for BMI calculation?
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For accurate BMI, measure height without shoes, standing against a wall with heels together. Use a stadiometer or mark the wall and measure with a tape. Height typically decreases by about 0.5-1 cm during the day due to spinal compression, so morning measurements are most accurate. Record height in centimeters or feet/inches.
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