What is a healthy BMI?

For most adults, 18.5 to 24.9 is considered the healthy range. But BMI is a general screen, not a diagnosis — context like muscle mass and waist size matters.

Why does my BMI seem high even though I'm fit?

BMI can't distinguish muscle from fat. Muscular, athletic people often score as 'overweight' despite being very healthy. Consider other measures alongside it.

Guides · 2026-05-07

How to Calculate Your BMI (And What It Actually Means)

Learn the BMI formula, how to calculate it in metric or imperial units, what the categories mean, and the limits of BMI as a health measure.

Try the free tool →

BMI — Body Mass Index — is one of the most widely used health numbers in the world. It's quick, free, and needs only your height and weight. But it's also widely misunderstood. Here's how to calculate it and, just as importantly, how to interpret it sensibly.

The formula

BMI is your weight divided by the square of your height:

Metric: BMI = weight (kg) ÷ [height (m)]²
Imperial: BMI = 703 × weight (lb) ÷ [height (in)]²

For example, someone 1.80 m tall weighing 75 kg has a BMI of 75 ÷ (1.80 × 1.80) = 75 ÷ 3.24 ≈ 23.1.

The standard categories (adults)

Under 18.5 — underweight
18.5 to 24.9 — normal / healthy weight
25 to 29.9 — overweight
30 and above — obese

What BMI is good for

BMI is a fast screening tool for populations and a reasonable first check for individuals. At scale, higher BMI correlates with higher risk of conditions like type 2 diabetes and heart disease, which is why doctors and researchers use it as a starting signal.

Where BMI falls short

BMI only knows your height and weight — it can't tell muscle from fat or where fat is stored. That leads to real blind spots:

Muscular people (athletes, weightlifters) often read "overweight" despite low body fat.
Older adults may lose muscle and carry more fat at the same BMI.
It doesn't account for waist size, which matters for health risk.

That's why BMI should be a conversation starter, not a diagnosis. Waist circumference, body-fat percentage, blood work, and a professional's assessment give the full picture.

Calculate yours privately

Use the free BMI Calculator — switch between metric and imperial, enter your height and weight, and see your BMI and category instantly. Your numbers stay in your browser and are never uploaded.

This article is general information, not medical advice. For guidance about your health, talk to a qualified professional.