BMI Calculator

Calculate your Body Mass Index (BMI) from your height and weight. Find out which health category you fall into and see the healthy weight range for your height.

Last updated: 2026-03-06

BMI calculator

Enter your values

Enter your height and weight to calculate your BMI.

Your BMI

Enter your height and weight to see your BMI.

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Example calculations

Tap an example to prefill the calculator with sample values.

Average US Male

5'9", 200 lb (imperial)

The average American man is 5 feet 9 inches and weighs about 200 pounds.

Result: BMI 29.5 — Overweight

Average US Female

5'4", 170 lb (imperial)

The average American woman is 5 feet 4 inches and weighs about 170 pounds.

Result: BMI 29.2 — Overweight

Healthy Range Example

5'7", 150 lb (imperial)

A person in the normal BMI range for their height.

Result: BMI 23.5 — Normal weight

Metric Example

175 cm, 80 kg

Using metric units for height in centimeters and weight in kilograms.

Result: BMI 26.1 — Overweight

Underweight Check

5'10", 125 lb

Checking whether a lighter individual falls below the healthy BMI range.

Result: BMI 17.9 — Underweight

Athlete Example

6'0", 210 lb

A muscular athlete may have a high BMI despite low body fat. BMI doesn't distinguish muscle from fat.

Result: BMI 28.5 — Overweight

How BMI Is Calculated

Body Mass Index (BMI) is a simple screening tool that estimates body fat based on your height and weight. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI remains one of the most widely used health metrics by doctors, insurers, and public health organizations worldwide. While it doesn't directly measure body fat, BMI correlates with more direct measures of body fat like skinfold thickness and underwater weighing.

The BMI Formula

BMI = weight (kg) ÷ height (m)². For imperial units, the formula is BMI = (weight (lb) × 703) ÷ height (in)². A 5'7" person weighing 150 pounds has a BMI of (150 × 703) ÷ (67²) = 23.5, which falls in the normal range. The 703 multiplier converts from imperial to the metric-based result.

BMI Categories

The World Health Organization classifies BMI into four main categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25.0–29.9), and Obese (30.0 and above). These thresholds were established based on epidemiological studies linking BMI ranges to health outcomes including cardiovascular disease, diabetes, and mortality risk.

Limitations of BMI

BMI does not distinguish between muscle and fat mass. Athletes and muscular individuals may have a high BMI despite having low body fat. BMI also doesn't account for age, sex, ethnicity, or body fat distribution — where you carry fat matters as much as how much you carry. Waist circumference and waist-to-hip ratio can provide additional context. Always consult a healthcare provider for a complete health assessment.

BMI reference chart

Below 18.5 — Underweight
18.5 – 24.9 — Normal weight
25.0 – 29.9 — Overweight
30.0 and above — Obese

BMI calculator FAQs

Answers to common questions about Body Mass Index.

What is a healthy BMI range?

A healthy BMI is between 18.5 and 24.9 according to the World Health Organization and the CDC. A BMI below 18.5 is considered underweight, 25.0–29.9 is overweight, and 30.0 or higher is classified as obese. However, BMI is just one indicator — your doctor may consider other factors like muscle mass, body fat distribution, age, and ethnicity.

Is BMI accurate for athletes or muscular people?

BMI can overestimate body fat in people with high muscle mass. Since muscle weighs more than fat per unit volume, athletes, bodybuilders, and physically active individuals may have a BMI in the overweight or obese range despite having a healthy body fat percentage. For these individuals, waist circumference, body fat percentage, or DEXA scans provide a more accurate picture.

What is the BMI formula?

For metric units: BMI = weight (kg) ÷ height (m)². For imperial units: BMI = (weight (lb) × 703) ÷ height (in)². The formula produces a number that correlates with body fat levels. For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75)² = 22.9.

Does BMI apply to children?

BMI is calculated the same way for children and adults, but interpreted differently. For children and teens (ages 2–20), BMI is compared against age-and-sex-specific growth charts to determine a percentile. A child at the 85th–94th percentile is considered overweight; 95th percentile and above is considered obese. This calculator is designed for adults.

How often should I check my BMI?

For most adults, checking your BMI once or twice a year is sufficient unless you're actively trying to gain or lose weight. More important than the number itself is the trend over time. If your BMI is trending upward, it may be worth discussing lifestyle changes with your healthcare provider before it enters an unhealthy range.

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Disclaimer

This BMI calculator is for educational and general informational purposes only. BMI is a screening tool and is not a diagnostic measure of body fat or health. Individual results may vary based on muscle mass, bone density, age, sex, and ethnicity. Consult a healthcare provider for a complete health assessment.