⚖️ Fitness Tool

BMI Calculator

Q: What is a healthy BMI?

A healthy BMI is between 18.5 and 24.9 according to the World Health Organization. Below 18.5 is underweight, 25–29.9 is overweight, and 30+ is obese.

Q: How is BMI calculated?

BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = weight(kg) / height(m)².

Q: Is BMI accurate for everyone?

BMI is a useful screening tool but does not account for muscle mass, bone density, or fat distribution. Athletes may have a high BMI despite low body fat.

Calculate your Body Mass Index (BMI) instantly. Enter your height and weight to find your BMI and see which WHO weight category you fall into.

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BMI Calculator

Height (cm)

Please enter a valid height (50–250 cm).

Weight (kg)

Please enter a valid weight (10–500 kg).

Age (years, optional)

Your BMI

BMI Range	Category	Risk
Below 18.5	Underweight	Increased
18.5 – 24.9	Normal weight	Low
25.0 – 29.9	Overweight	Moderate
30.0 – 34.9	Obese Class I	High
35.0 – 39.9	Obese Class II	Very High
40.0 and above	Obese Class III	Extremely High

What is BMI?

Body Mass Index (BMI) is a simple numerical measure of a person's body weight relative to their height. It was developed by the Belgian mathematician Adolphe Quetelet in the 1830s and is now used worldwide as a standard screening tool by doctors, public health authorities, and fitness professionals.

The World Health Organization (WHO) defines BMI categories for adults as: Underweight (<18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (≥30). These categories are associated with different health risks including heart disease, type 2 diabetes, and other chronic conditions.

BMI Formula

Metric: BMI = Weight (kg) ÷ [Height (m)]²
Imperial: BMI = 703 × Weight (lbs) ÷ [Height (inches)]²

Limitations of BMI

While BMI is a useful screening tool, it does not directly measure body fat. It may not be an accurate indicator for athletes (who have high muscle mass), elderly individuals (who may have lost muscle), or people with different body compositions. For a complete health assessment, consult your healthcare provider.

Frequently Asked Questions

What is a healthy BMI? +

A healthy BMI is between 18.5 and 24.9 according to the World Health Organization (WHO). This range is associated with the lowest risk of weight-related health problems. However, BMI is just one measure and should be considered alongside other health indicators.

How is BMI calculated? +

BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = kg/m². In imperial units, the formula is: BMI = 703 × lbs / inches². For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75²) = 22.9.

Is BMI accurate for everyone? +

BMI is a useful population-level screening tool but has limitations at the individual level. It doesn't account for muscle mass (athletes may have a high BMI with low fat), age, sex, or ethnicity. For example, Asian populations may face health risks at lower BMI thresholds. Always use BMI alongside other health assessments.