BMI Calculator

Calculate your Body Mass Index (BMI) instantly. Find out if you're at a healthy weight.

What Is BMI (Body Mass Index)?

Body Mass Index (BMI) is a widely used screening tool that measures body fat based on your height and weight. It provides a simple numeric indicator of whether you're at a healthy weight for your height.

BMI Formula

Metric: BMI = weight (kg) ÷ height² (m²)
Imperial: BMI = 703 × weight (lbs) ÷ height² (inches²)

BMI Categories

BMI RangeCategoryHealth Risk
Below 18.5UnderweightModerate
18.5 – 24.9Normal weightLow
25.0 – 29.9OverweightIncreased
30.0 – 34.9Obese (Class I)High
35.0 – 39.9Obese (Class II)Very High
40.0+Obese (Class III)Extremely High

Limitations of BMI

BMI doesn't account for muscle mass, bone density, or body composition. Athletes with high muscle mass may register as "overweight" despite being healthy. For a more complete picture, consider waist circumference and body fat percentage alongside BMI.

FAQ

Is BMI accurate for athletes?
BMI doesn't distinguish between muscle and fat. Very muscular individuals may have a high BMI but low body fat. If you're athletic, consider body fat percentage measurements instead.
What is a good BMI for my age?
For adults 20+, a BMI between 18.5 and 24.9 is considered healthy. For seniors (65+), a slightly higher BMI (23-30) may actually be protective.
How do I lower my BMI?
Sustainable weight loss combines a balanced, calorie-appropriate diet with regular exercise. Aim for 150 minutes of moderate activity weekly and consult a healthcare provider.
Does BMI work for children?
BMI for children (under 20) uses percentile ranges rather than fixed categories. Consult a pediatrician for age-specific assessments.
Is BMI different for men and women?
The BMI formula is the same, but women naturally carry more body fat at the same BMI. The categories, however, apply equally to both sexes.
Is BMI accurate for muscular individuals?
No. BMI cannot distinguish between muscle and fat. A bodybuilder weighing 220 lbs at 5'10' would have a BMI over 31 (obese) despite having very low body fat. For athletes or very muscular people, body fat percentage, waist circumference, and visual assessment are better health indicators than BMI.
What's a healthy BMI range for adults?
For adults aged 20–65, the standard categories are: under 18.5 = underweight, 18.5–24.9 = normal weight, 25.0–29.9 = overweight, 30.0+ = obese. For seniors 65+, some research suggests a slightly higher range (23–30) may be protective. Always discuss your specific situation with a healthcare provider.
Does BMI work for different ethnicities?
BMI was developed from European population data and may not perfectly apply to all ethnicities. Some Asian populations face health risks at lower BMIs (23+), which is why some countries use modified thresholds. People of Polynesian descent may have higher BMIs without equivalent health risk due to naturally higher muscle mass. Consult your doctor for personalized guidance.
Should I rely on BMI alone for health assessment?
No. BMI is a useful screening tool but has significant limitations. For a complete health picture, combine it with body fat percentage, waist circumference, blood pressure, cholesterol levels, blood sugar, and physical fitness assessments. A healthcare provider can interpret these together for personalized guidance.

How to Use the BMI Calculator

  1. Select your unit system — metric (centimeters, kilograms) or imperial (inches, pounds).
  2. Enter your height and weight in the appropriate units for your selected system.
  3. Provide your age and gender — this gives context for interpreting your BMI result.
  4. Click "Calculate BMI" to instantly see your BMI value, category (underweight, normal, overweight, or obese), and healthy weight range for your height.
  5. Review your healthy weight range — the calculator shows the weight range corresponding to a BMI of 18.5–24.9 for your height.

Using BMI for Health Assessment

BMI (Body Mass Index) is a quick screening tool developed in the 1830s by Belgian mathematician Adolphe Quetelet. It correlates reasonably well with body fat percentage for populations, which is why organizations like the WHO and CDC use it for public health statistics. For most adults aged 20–65, BMI provides a useful first-pass health indicator. However, its limitations are well-documented: it doesn't distinguish between fat mass and muscle mass, doesn't account for fat distribution (visceral belly fat is more dangerous than subcutaneous fat), and becomes less accurate for the elderly (who lose muscle mass) and very tall or short individuals.

Research increasingly shows that where you carry fat matters as much as how much you carry. Waist-to-hip ratio and waist circumference are stronger predictors of cardiovascular disease than BMI alone. A waist circumference above 40 inches (102 cm) for men or 35 inches (88 cm) for women indicates elevated health risk regardless of BMI. For a more complete health picture, combine BMI with body fat percentage, waist measurements, and blood markers like cholesterol and blood sugar. Always discuss your results with a healthcare provider rather than self-diagnosing based on BMI alone.

For children and teens under 20, BMI is interpreted using percentile ranges rather than fixed categories, because body composition changes dramatically during growth. A child's BMI is compared to others of the same age and gender, with the 5th–85th percentile considered healthy weight. For adults 65 and older, some studies suggest that a slightly higher BMI (23–30) may actually be protective, providing energy reserves during illness. Athletes with high muscle mass may have BMIs in the "overweight" range despite being lean and healthy — this is BMI's most well-known blind spot.

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