What Your BMI Does — and Doesn't — Tell You
BMI gets a bad rap these days, and some of the criticism is fair. But it's still one of the quickest ways to get a rough read on whether your weight is in a healthy range for your height. The trick is knowing what it's good for — and where it stops being useful.
How the number is built
BMI is just your weight in kilograms divided by your height in metres squared. A person who is 1.7 m tall and weighs 70 kg has a BMI of about 24.2. The World Health Organization buckets the result into bands: below 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight, and 30 or above is in the obesity range.
What it's genuinely good at
At a population level, BMI is excellent. It's cheap, instant, needs no equipment, and correlates well with health risks across large groups of people. For a quick personal check — am I roughly where I should be? — it does the job in seconds.
Where it falls down
BMI doesn't know the difference between muscle and fat. A lean, heavily-trained athlete can land in the "overweight" band purely because muscle is dense. It also says nothing about where you carry weight, and fat around the midsection carries more risk than fat elsewhere. Age, sex, and ethnicity all shift the picture too — which is why some guidelines use lower thresholds for South Asian populations.
Use it as one signal among several
Think of BMI as the first line of a report, not the conclusion. Pair it with simpler real-world checks: how your clothes fit, your waist measurement, your energy levels, your blood markers at a routine check-up. If your BMI flags something and those other signals agree, that's worth acting on. If you're strong, active, and your bloodwork is clean, a slightly "high" BMI is far less concerning than the single number suggests.
Curious where you currently sit? Our BMI Calculator gives you the number and the WHO category in one step — just remember it's a starting point for a conversation, not the final word.
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