BMI Calculator
Calculate your Body Mass Index and understand your health metrics.
About the Toolers BMI Calculator
Body mass index compares weight against height using a single formula, giving a quick population-level screening figure. The Toolers BMI Calculator accepts metric or imperial units, returns your index to one decimal place, and shows which of the standard categories that value falls into so the number means something without a separate reference chart.
BMI became popular because it needs only two measurements that anyone can take at home, and because large studies found correlations between BMI bands and certain health risks across populations. That is its strength and also its limit: it describes groups well and individuals only roughly.
Reading the categories properly
The conventional adult bands are below 18.5 for underweight, 18.5 to 24.9 for the healthy range, 25 to 29.9 for overweight and 30 or above for obesity. Some health authorities apply lower thresholds for people of South Asian descent because cardiometabolic risk appears at lower indices. Bands are boundaries on a continuum, so a value one tenth either side of a line is not a meaningful difference.
Where BMI misleads
The formula cannot tell muscle from fat, and it ignores where weight sits on the body. Athletes with high lean mass often score as overweight while carrying very little fat. Older adults may score in the healthy band while having lost muscle. Waist circumference, waist-to-height ratio and body composition measurements add the context BMI lacks, and none of them replace a conversation with a clinician.
Frequently asked questions
Not in this form. Children and teenagers are assessed against age and sex percentile charts rather than fixed adult thresholds, so a paediatric calculator should be used instead.