What BMI tells you
Body Mass Index is a simple screening number: your weight in kilograms divided by your height in metres squared. Health organisations use it because it is fast and works reasonably well across large populations. For most adults, 18.5-24.9 is labelled the healthy range, 25-29.9 is overweight, and 30 or above is the obesity range.
What BMI does not tell you
BMI cannot show what your weight is made of. Muscle is denser than fat, so a muscular person can score "overweight" while being lean. It also says nothing about where fat sits, how you eat, how you move, or how you feel. Those details matter far more for long-term health than one ratio.
The DietPattern view: measure it once, note it, and move on. Day-to-day habits, including when you eat, what you reach for, and how regularly meals happen, shape health more than repeatedly checking a number. That is what DietPattern helps you notice, without counting.
If your number surprised you
- Do not react to one data point. Weight can naturally fluctuate 1-2 kg within a week because of water, salt, and routine changes.
- Look at patterns, not restriction. Skipped breakfasts, late-night eating, and irregular meal times move weight more than most people expect. A week of simply logging meals usually reveals one obvious, fixable habit.
- Talk to a professional for real guidance. A doctor or registered dietitian can interpret BMI alongside everything it can't see.
Frequently asked questions
How is BMI calculated?
Weight (kg) / height (m)2. In imperial units: weight (lb) / height (in)2 x 703. This calculator handles both automatically.
What is a healthy BMI?
18.5–24.9 for most adults. Ranges differ for children, during pregnancy, and in some populations — another reason to treat it as a starting point.
Is BMI accurate for everyone?
No. It is a population-level screening tool. Athletes, older adults, and very tall or short people are common cases where it can mislead.
Does this calculator store my data?
No. It runs entirely in your browser; nothing is sent or saved.