BMI is a simple ratio of weight to height. It can be a helpful starting point when you want a broad screening measure, but it is not a complete picture of someone’s health.

The calculation does not distinguish between muscle and body fat. A person who trains regularly and carries a lot of muscle may have a higher BMI without having a high level of body fat. Age, ethnicity, waist measurement, medical history and day-to-day habits can also matter.

That does not make BMI useless. It can be helpful when tracked over time, especially if it is considered alongside other information. A steady change can prompt a useful conversation about diet, activity, sleep or medical support.

Use the BMI Calculator for a quick estimate, then keep the result in context. If a result concerns you, or if you are managing a health condition, speak with a qualified healthcare professional rather than relying on a single number.