BMI is a quick screening number that compares your weight to your height. It's useful at a population level and as a starting point — but it's a rough tool, and it doesn't measure health directly.
The standard categories
| BMI range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obesity |
These ranges come from large population studies linking BMI bands to average health outcomes. They describe groups well — but any individual can sit outside the average.
What BMI gets right
It's fast, free, needs only height and weight, and tracks reasonably well across large populations. For most people it's a sensible first flag worth discussing with a doctor.
What BMI can't see
- Body composition — muscle weighs more than fat for the same size.
- Fat distribution — waist measurement adds important context.
- Age, sex and ethnicity — risk thresholds genuinely differ across groups.
- Fitness and metabolic health — blood pressure, blood sugar and activity matter independently of BMI.
Better used as one signal among several
Treat BMI as a conversation-starter, not a verdict. Paired with a waist measurement, your activity level, and basic bloodwork, it becomes far more meaningful. Calculate yours, then bring the number — and its context — to your next check-up.
This article is general information, not financial, tax, or medical advice. See our disclaimer.