BMI Calculator — Body Mass Index for Adults

Calculate your Body Mass Index (BMI) instantly using metric (kg/cm) or imperial (lbs/inches) units. Find out if you're underweight, normal weight, overweight, or obese based on WHO guidelines.

BMI is a widely used screening tool for weight categories that may lead to health problems. Use it alongside other health indicators for a complete picture of your health.

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Select units and enter your measurements

Weight (kg)

Height (cm)

Enter your weight and height above to calculate your BMI instantly.

BMI is a screening tool, not a diagnostic measure. Consult a healthcare professional for medical advice. BMI may not be accurate for athletes, elderly, or pregnant women.

What is BMI and How Is It Calculated?

Body Mass Index (BMI) is a numerical value calculated from your weight and height. It provides a simple, inexpensive screening method for weight categories — underweight, healthy weight, overweight, and obesity — that may be associated with health problems.

BMI Formula (metric): BMI = weight (kg) ÷ height² (m²)
Example: 70kg ÷ (1.75m × 1.75m) = 70 ÷ 3.0625 = 22.9 — Normal weight

BMI categories (WHO standard)

Underweight: BMI below 18.5
Normal weight: BMI 18.5–24.9
Overweight: BMI 25.0–29.9
Obese Class I: BMI 30.0–34.9
Obese Class II: BMI 35.0–39.9
Obese Class III: BMI 40.0 and above

Limitations of BMI

BMI does not distinguish between muscle and fat mass. A muscular athlete may have a high BMI but low body fat. Similarly, an older person may have a normal BMI but high body fat percentage. BMI also does not account for fat distribution — belly fat is more dangerous than fat stored elsewhere. Use BMI as one of several indicators of health, not as the sole measure.

For children and teenagers, BMI is calculated differently using age and sex-specific percentiles. This calculator is designed for adults aged 18 and over.

Frequently Asked Questions

What is a healthy BMI?

According to the World Health Organization (WHO), a BMI between 18.5 and 24.9 is considered healthy for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese. These are general guidelines — individual health depends on many factors beyond BMI.

Is BMI accurate for everyone?

BMI is a useful screening tool but has limitations. It can overestimate body fat in athletes and muscular people, and underestimate it in older adults who have lost muscle mass. It also doesn't account for fat distribution. For a complete health assessment, consult a healthcare professional.

How do I calculate BMI in pounds and inches?

BMI (imperial) = (weight in lbs × 703) ÷ height in inches². For example: 154 lbs, 5ft 9in (69 inches): (154 × 703) ÷ (69 × 69) = 108,262 ÷ 4,761 = 22.7. This calculator does this automatically when you select Imperial units.

How much should I weigh for my height?

Use this BMI calculator — the results show your healthy weight range for your height. For example, for a height of 5ft 10in (178cm), the healthy weight range is approximately 60–79 kg (132–174 lbs), corresponding to a BMI of 18.5–24.9.

Can children use this BMI calculator?

No — this calculator is designed for adults aged 18 and over. Children and teenagers need a different BMI calculation that accounts for age and sex using percentile charts. Use the CDC's BMI calculator for children and teens.