Completely FREE BMI calculator. No signup, instant result. Enter your height and weight in either imperial (feet, inches, pounds) or metric (centimeters, kilograms) units and get your body mass index, its standard category, and the weight range considered healthy for your height. It updates as you type.
Your data never reaches us
Nifty Utilities has no backend server, database, user accounts, or endpoint capable of receiving your tool inputs. Files and entries are processed inside your browser. We cannot view, capture, or store them.
What BMI is
Body mass index is a single number derived from your height and weight — weight in kilograms divided by height in meters squared. It was designed as a quick population-level screening figure, a rough way to sort people into broad weight categories without measuring anything more involved. The standard adult bands are: below 18.5 underweight, 18.5 to 24.9 healthy weight, 25 to 29.9 overweight, and 30 or above obesity. This calculator shows your number, the band it falls in, and the weight range that would put you in the healthy band at your height.
What BMI is not
BMI is genuinely useful as a starting point and genuinely limited as an endpoint, and being honest about both is important. It does not distinguish muscle from fat, so a muscular athlete can register as "overweight" while carrying very little fat. It says nothing about where fat is stored, which matters more for health than the total. And it was largely derived from particular populations, so it can misjudge people of different ages, sexes, ethnicities, and body frames. Two people with the same BMI can be in very different health. Treat the number as one rough input among many, not a verdict.
Imperial or metric — same math
Switch the units toggle and the fields change to match: feet-and-inches with pounds, or centimeters with kilograms. The tool converts internally to the metric formula, so the result is identical either way — enter whichever units you actually know your measurements in. The healthy-weight range is shown back in the units you selected, so it's immediately usable.
Using it sensibly
BMI is best read as a prompt for a conversation, not a conclusion. If your number sits outside the healthy band, that's a reason to look at the fuller picture — waist measurement, activity, diet, family history, and lab work — ideally with a clinician who can weigh all of it. If it sits inside the band, that's reassuring but not a clean bill of health on its own. The number is a screening tool doing exactly one small job.
Runs entirely in your browser — and privately
Health numbers are sensitive, and this calculator is built so they stay yours: the math runs in your browser and nothing you enter is transmitted or stored anywhere. There's no account and no tracking of what you type. For a different kind of self-check, the site also has a Reaction Time Test and other quick browser-based tests.
Frequently asked questions
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is the standard "healthy weight" range. The calculator also shows the actual weight range that corresponds to that band for your specific height.
Is BMI accurate for athletes or very muscular people?
Not reliably. BMI can't tell muscle from fat, so a muscular person may score as "overweight" despite low body fat. For those cases, body-composition measures are more meaningful than BMI alone.
Is this medical advice?
No. BMI is a general screening number, not a diagnosis, and this tool is not medical advice. Talk to a qualified healthcare professional about what your result means for your health.
Important
BMI is a general screening figure, not a diagnosis or a measure of body fat, fitness, or health. It does not account for muscle mass, body composition, frame, age, sex, or ethnicity. It is not medical advice — consult a qualified healthcare professional about what a result means for you.
Support
Problem with this tool or suggestions for improvement? Please email support@niftyutilities.com.