BMI Calculator — Body Mass Index Calculator

Calculate your Body Mass Index instantly. Free, no signup required.

Body Mass Index (BMI) is a screening tool that estimates whether your weight is appropriate for your height. It is calculated by dividing weight in kilograms by height in metres squared. A BMI between 18.5 and 24.9 is considered normal for most adults. BMI is a useful first indicator but has well-known limitations — it does not distinguish muscle from fat, and may misclassify athletes as overweight or older adults with low muscle mass as healthy. For a complete picture of health, BMI should be considered alongside waist circumference, body fat percentage, and medical history.

Height (cm)

Weight (kg)

BMI RANGES

Below 18.5Underweight

18.5 – 24.9Normal weight

25.0 – 29.9Overweight

30.0+Obese

BMI is a general indicator and does not account for muscle mass, age, or other health factors. Consult a doctor for a full health assessment.

Understanding Your BMI Result

BMI is calculated by dividing your weight in kilograms by the square of your height in metres. It is used globally as a quick screening tool for weight-related health risks.

Under 18.5 — Underweight: May indicate nutritional deficiency. A doctor can assess whether weight gain is advisable.

18.5 to 24.9 — Normal weight: Associated with the lowest risk of weight-related conditions for most adults.

25.0 to 29.9 — Overweight: Elevated risk for type 2 diabetes, high blood pressure, and cardiovascular disease.

30.0 and above — Obese: Significantly elevated health risk. Medical guidance alongside dietary and activity changes is recommended.

Limitations of BMI

BMI does not distinguish between muscle and fat. A professional athlete may register as overweight despite having very low body fat. Conversely, an elderly person with low muscle mass may have a normal BMI but unhealthy body composition.

BMI also does not account for how fat is distributed in the body. Abdominal fat carries higher cardiovascular risks than fat stored around the hips. Use BMI alongside waist circumference measurements and consult a healthcare professional for a complete assessment.

Frequently Asked Questions

What is BMI?

BMI or Body Mass Index is a measure of body fat based on height and weight. It is calculated by dividing weight in kg by height in meters squared.

What is a healthy BMI range?

A BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25-29.9 is overweight and 30 or above is obese.

Is BMI accurate for everyone?

BMI is a general screening tool and does not account for muscle mass, age, gender or body composition. Athletes may have high BMI despite low body fat.

How often should I check my BMI?

Checking BMI once or twice a year is sufficient for most people unless you are actively working on weight management.

Does BMI differ for children?

Yes. BMI for children uses age and sex specific percentiles rather than fixed ranges used for adults.