Adult BMI Calculator

Calculate a qualified adult BMI reference

1. Check this page's scope before entering measurements. It is for adults 20 and older, not for pregnancy, a diagnosed or suspected eating disorder, or a condition affecting height. It does not collect age or medical details to decide whether you are eligible.
2. Choose Metric for centimetres and kilograms, or US customary for feet, inches and pounds. Enter the active measurements, then select Calculate. Inches can be zero but total height must be positive. Changing profiles restores separate drafts; it does not convert them.
3. Read the approximate BMI and standard category with the adjacent limitations. A note explains when display rounding reaches a category boundary but the unrounded value has not. Copy includes the current inputs and qualifications. Editing removes the old result; Clear resets both profiles.

What the index and category mean

BMI is weight in kilograms divided by height in metres squared. It is a screening reference based on two measurements, not a direct measurement of body fat. It cannot distinguish fat, muscle and bone or describe where fat is carried; individual assessment uses other information.

The standard adult categories used here are Underweight below 18.5, Healthy weight from 18.5 to below 25, Overweight from 25 to below 30, and Obesity at 30 or above. They classify the unrounded index, not the one-decimal display. Healthy weight is the category name, not assurance of good health.

US measurements are normalized with the exact definitions of 0.0254 metres per inch and 0.45359237 kilograms per pound. The familiar shortcut factor 703 is rounded and can give a different category close to a cutoff. Internal conversion never overwrites the other profile's drafts.

Body composition and population context affect interpretation. Muscular people can have a higher BMI without the same body-fat pattern, and some ethnic backgrounds can experience health problems at lower BMI values. This tool does not personalize thresholds, predict disease or replace an appropriate individual assessment.

Ordinary and boundary examples

At 170 cm and 70 kg, BMI is approximately 24.2 and falls in the standard Healthy weight category. The category alone does not establish a person's overall health. Use example fills these measurements, ready for you to calculate.

At 200 cm and 99.96 kg, the unrounded BMI is 24.99. The one-decimal display is 25.0, but the standard category remains Healthy weight because the unrounded value is below 25. The result includes a near-cutoff explanation instead of silently reclassifying it.

At 5 ft 9 in and 169.3 lb, exact unit conversion gives a BMI just above 25, in the standard Overweight category. The rounded 703 shortcut gives a value just below 25. This illustrates why the calculation method and unrounded boundary matter; neither category supplies a personal health verdict.

Scope and interpretation limits

This page deliberately starts at age 20, matching CDC adult category routing. The NHS adult service starts at 18; our narrower scope does not mean ages 18–19 cannot be assessed elsewhere. Do not use this page during pregnancy, with a diagnosed or suspected eating disorder, or with a condition affecting height. No age or diagnosis is inferred from measurements.

There are no child or teen percentiles, obesity subclasses, ethnicity-adjusted thresholds, waist measures, body-fat estimates, target weights or treatment, calorie or exercise recommendations. Standard categories are not identical to personal risk, and the result is neither diagnosis nor proof of health.

Decimal fields accept at most two fractional digits with a dot or comma and no thousands separators; feet is an integer. Each raw field is limited to 32 UTF-16 units. The stated bounds keep arithmetic finite, not clinically validated. A positive BMI too small for a one-decimal result is shown as less than 0.1, never zero.

Keep control of sensitive measurements

This tool does not upload height or weight, add measurements to a shareable URL or save them in browser storage. Drafts last only while the tool is open; age, sex, ethnicity and medical history are not collected. Copy shares the current qualified text only when you choose it. These tool-specific choices do not certify the whole site's analytics behavior.