Adult BMI uses fixed ranges, but it does not diagnose a condition by itself.
Adult screening
BMI Calculator
Calculate your BMI free — metric, US or stone units, with healthy-weight range and formula shown. Private, no signup. Not medical advice.
Not medical advice
This calculator gives general screening information only. It is not medical advice or a diagnosis.
20+For adults age 20 and older
Your measurements stay in this browser.
Read the result
One number, read in context.
Muscle mass, fat distribution, pregnancy and other individual factors affect interpretation.
This page is for ages 20+. Children and teens need age- and growth-chart-specific BMI interpretation.
BMI, BFP, BMR and TDEE answer different questions.
A screening measure of weight relative to height. CDC uses it for adult weight categories; it does not directly measure body fat.
Body-fat percentage. Here it is estimated from BMI, age and an equation reference, not measured by DEXA or another direct body-composition test.
An estimate of energy needed to maintain basic function at rest. This page uses a published resting-energy prediction equation, not a measurement.
A rough estimate of 24-hour energy expenditure, including rest, the thermic effect of food and activity; it is not a nutrition prescription.
Adult BMI chart and healthy BMI
BMIScreening range
<18.5Underweight
18.5–<25Healthy weight
25–<30Overweight
≥30Obesity
These are CDC BMI categories for adults age 20 and older; the Healthy Weight BMI range is 18.5 to less than 25.
What are the limitations of BMI?
- BMI does not directly measure body fat.
- Higher muscle mass can raise BMI.
- Waist measurement can add context about fat distribution.
- Pregnancy, age, body composition and other factors can change interpretation.
BMI and waist measurement
BMI does not show fat distribution. Waist information measured consistently can add context about central adiposity, but it is also not a diagnosis.
Does BMI work for athletes?
BMI cannot distinguish muscle from fat, so it can overstate body-fat-related risk when muscle mass is high. It cannot answer an individual health question on its own.
Frequently asked questions
How is BMI calculated?
BMI is weight divided by height squared. This calculator shows the formula and supports metric, US customary, and stone-based inputs.
Is BMI accurate?
BMI is a screening measure, not a diagnosis. It does not account for every factor such as muscle mass, age, health history, or body composition.
Can children use this BMI calculator?
No. This page is designed for adults. Children and teens need age- and sex-specific growth references interpreted by a qualified professional.
Is my data saved?
No. Your measurements and result are calculated locally in this browser and are not saved by ToolkitLoop.
Rules you can check, not authority we invent.
AlgorithmAdult BMI v1.1.0
BMI, adult BFP and resting-energy formulas are documented in the sources below.
Age scopeBMI: age 20+
Optional BFP, BMR and TDEE estimates are limited to ages 20–78, the shared age range studied by both equations.
Last source reviewSeptember 2, 2026
Policy: check source availability quarterly; manually review formulas at least annually and sooner after a material change in cited guidance. Automated checks never change calculations.
CDC Adult BMI Categories ↗CDC BMI formula ↗CDC: About BMI ↗PubMed: adult BFP equation ↗PubMed: Mifflin–St Jeor equation ↗National Academies: daily energy expenditure ↗
This calculator provides general screening and estimation information. BMI does not diagnose health conditions or directly measure body fat; BFP, BMR and TDEE are not body-composition tests, measured metabolism or nutrition prescriptions. Pregnancy, childhood and adolescence, eating disorders, metabolic conditions and other health questions need discussion with a qualified healthcare professional.
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