BMI Calculator

Body Mass Index (BMI) is one of the most widely used screening tools for categorizing weight status. Enter your height and weight to get your BMI score, understand which category you fall into, and learn what the number really means for your health.

What Is BMI and Why Does It Matter?

Body Mass Index (BMI) is a numerical value derived from your weight and height. It was developed in the early 19th century by Belgian mathematician Adolphe Quetelet as a quick way to gauge whether a person's weight is proportionate to their height. Today, healthcare professionals, insurers, and public-health organizations use BMI as a first-pass screening tool for weight-related health risks.

While BMI does not directly measure body fat, research shows a moderate correlation between BMI and more direct measures of adiposity such as DEXA scans. A high BMI is statistically associated with greater risk of type 2 diabetes, cardiovascular disease, and certain cancers, making it a useful population-level indicator.

The Formula

BMI is calculated using the following formula:

Metric: BMI = weight (kg) / height (m)²
Imperial: BMI = (weight (lbs) × 703) / height (in)²

How to Interpret Your Results

BMI Range	Category
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25.0 – 29.9	Overweight
30.0 – 34.9	Obesity Class I
35.0 – 39.9	Obesity Class II
40.0 and above	Obesity Class III

Limitations

BMI does not distinguish between muscle mass and fat mass. Athletes, bodybuilders, and individuals with high lean mass may register as overweight or obese despite having low body-fat levels. Additionally, BMI does not account for fat distribution; visceral fat around the abdomen is more dangerous than subcutaneous fat elsewhere. For a more complete picture, combine BMI with body-fat percentage, waist-to-hip ratio, and clinical assessments. Always consult a healthcare professional before making major lifestyle changes based solely on your BMI.

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Frequently Asked Questions

What is a healthy BMI range for adults?

A BMI between 18.5 and 24.9 is generally considered the healthy range for adults. However, individual factors such as muscle mass, bone density, and ethnicity can influence what is truly healthy for you. Consult a doctor for personalized advice.

Does BMI accurately reflect body fat?

BMI is a screening tool, not a diagnostic measure of body fat. It correlates moderately with body-fat percentage at the population level but can misclassify muscular individuals as overweight. Pairing BMI with a body-fat measurement gives a more accurate picture.

Is BMI different for men and women?

The BMI formula and standard categories are the same for men and women. However, women naturally carry more body fat than men at the same BMI, so some experts advocate for sex-specific interpretations. Additional metrics like body-fat percentage help fill in the gaps.

How often should I check my BMI?

Checking your BMI once every few months is sufficient for most people. Frequent weigh-ins can cause unnecessary stress and do not reflect short-term fluid fluctuations. Track trends over time rather than focusing on any single measurement.