Adult BMI & Reference Weight Range Calculator.

Formula or algorithm and variables.

Equation, units, and population

BMI = weight kg ÷ height metres²; reference weight = BMI boundary × height metres². The category labels and 18.5 to less than 25 reference interval are the CDC adult screening ranges for people age 20 and older. This page names the equation rather than presenting an unexplained score. Check that every value uses the displayed unit and that you belong to the population for which the method is described. The calculation retains full precision internally and rounds only the visible result. A reproducible estimate should let another reader use the same inputs and reach the same arithmetic answer, while still recognizing that mathematical reproducibility does not prove medical suitability.

Worked example

A person who is 70 kg and 1.75 m tall has BMI 70 ÷ 1.75² = 22.9. At that height, the adult 18.5–24.9 reference interval corresponds to approximately 56.7–76.3 kg. Work through the example by writing the equation, substituting each labeled input, and preserving units at every step. The example demonstrates arithmetic only; it is not a recommended body measurement, intake, exercise level, laboratory value, or date. Replace every example input with the values from the situation being considered, and retain those inputs with any result you copy. Small differences can arise from rounding, equation versions, atomic-weight conventions, or date boundaries.

Interpreting the estimate

The category and reference interval are population screening context. They are not a prescribed target, and a clinician may prioritize other measurements and health history. Health calculations compress complex biology into a few inputs, so the result should be read as context rather than a verdict. Do not compare two people as though the higher or lower number is automatically better. Look for changes over time only when the method, units, and conditions are consistent. If a result conflicts with symptoms, a laboratory report, a clinician’s instructions, or a validated measurement, rely on the appropriate professional evidence rather than this calculator.

Validation and edge cases

This page is restricted to ages 20–120, height 100–250 cm, and weight 20–400 kg. Pregnancy is excluded by the visible guidance rather than inferred from personal data. Blank, malformed, nonfinite, and out-of-domain inputs fail explicitly without producing NaN or infinity. The bounds prevent obviously implausible values from being mistaken for meaningful answers, but passing a range check does not make an input medically correct. Recheck dates, decimal separators, unit conversions, coefficient choices, and whether a laboratory value uses the expected assay and unit. Contact a qualified professional when a result could affect treatment, medication, pregnancy care, nutrition therapy, or exercise safety.

Limitations and responsible use

The adult categories are not for pregnancy and are not the appropriate child or teen growth-chart method. Muscularity, age, ethnicity, disability, and body composition can change interpretation. BMI is a screening measure, not a diagnosis or a judgment about a person. It does not directly measure body fat, health, fitness, or worth. FigureNest processes these inputs locally in the browser and does not send them to a calculation service. The page does not create a medical record, assess symptoms, or know personal history. Avoid using estimates to shame a body, pursue unsafe restriction, delay care, determine legal fitness, or replace contraception. Authoritative source links are provided so readers can check the equation version and current guidance before making a consequential decision.

Check assumptions and sources.

The adult categories are not for pregnancy and are not the appropriate child or teen growth-chart method. Muscularity, age, ethnicity, disability, and body composition can change interpretation.

CDC Adult BMI Categories