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BMI CalculatorMobile Tool Mode
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Calculate BMI without loading the full page first.
This guided phone experience calculates adult BMI, the standard category, and a healthy-weight range for the entered height.
What you will need
Your current height and weight in U.S. or metric measurements.
01
Choose a measurement system.
02
Enter height and weight in focused steps.
03
Review the result and useful tracking offers.
Private by design: Calculations run in this browser. Height and weight are not sent to MegaTools.tools.
Choose your measurement system.
Select the units you normally use.
Enter your height.
The healthy-weight range is calculated from this measurement.
ft
in
cm
Enter your current weight.
Use a recent measurement when possible.
lb
kg
Your BMI estimate.
Use the result as a screening number, not a diagnosis.
Calculated adult BMI—
—
Adult category—
Healthy-weight range—
BMI is based only on height and weight.
Helpful tracking optionsDigital Bathroom Scales Body Measuring Tapes
Record waist and other measurements for added context beyond BMI.
Shop Body Measuring TapesAs an Amazon Associate I earn from qualifying purchases. Prices and availability can change.
Health note: BMI does not distinguish fat from muscle or bone and does not replace an individual health assessment.
Free Adult BMI Calculator
BMI Calculator with U.S. and metric measurements.
Calculate body mass index from height and weight, see the standard adult category, and estimate the healthy-weight range associated with the entered height.
Step 1 · Enter height and weight
Calculate adult BMI
This calculator uses the standard adult BMI formula and categories for adults age 20 and older.
What the result means
BMI is a screening number—not a diagnosis.
Body mass index compares weight with height. It can help identify a weight category, but it cannot explain body composition, fitness, nutrition, medical history, or an individual health risk by itself.
Height and weight
BMI uses only these two measurements. The metric formula is weight in kilograms divided by height in meters squared.
Adult category
The result is compared with standard adult ranges: underweight, healthy weight, overweight, and obesity.
Healthy-weight estimate
The tool also calculates the weights at the entered height that correspond with BMIs from 18.5 through 24.9.
Method and privacy: The calculation runs in your browser. Height and weight entered on this page are not sent to MegaTools.tools or saved to an account. U.S. BMI is calculated as weight in pounds divided by height in inches squared, multiplied by 703. Metric BMI is kilograms divided by meters squared.
Adult BMI categories
Standard ranges for adults age 20 and older.
The calculator uses the conventional adult BMI thresholds. Obesity is separated into three classes to provide a more specific category.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 to less than 25 |
| Overweight | 25 to less than 30 |
| Obesity — Class 1 | 30 to less than 35 |
| Obesity — Class 2 | 35 to less than 40 |
| Obesity — Class 3 | 40 or higher |
Important context: Adult BMI categories are not used the same way for children and teenagers. People age 2 through 19 are assessed with age- and sex-specific BMI percentiles. Pregnancy, athletic muscle mass, older age, fluid retention, limb differences, and some medical conditions can also make BMI less informative for an individual.
Helpful health-tracking tools
Track measurements more consistently.
BMI is only one screening number. A reliable scale and measuring tape can help you record changes over time and discuss clearer information with a healthcare professional when needed.
Amazon Associate disclosure: As an Amazon Associate I earn from qualifying purchases. Prices and availability can change after you leave MegaTools.tools.
Digital Bathroom Scales
Useful for checking body weight consistently at home. Look for a clear display, stable platform, and a weight capacity that fits your needs.
For general home tracking—not a medical device recommendation.
Check Digital Scales on Amazon
Body-Composition Scales
These scales may display estimates such as body-fat percentage, muscle mass, or water weight in addition to body weight.
Consumer body-composition estimates can vary and should not replace clinical testing.
See Body-Composition Scales
Body Measuring Tapes
A flexible measuring tape can help record waist, hip, arm, thigh, or other measurements using the same position and method each time.
Measure gently and consistently without pulling the tape tightly.
Shop Body Measuring Tapes
Related health tools
Continue the health calculation.
Common questions
BMI calculator questions.
What is the formula for BMI?+
Using metric measurements, BMI equals weight in kilograms divided by height in meters squared. Using U.S. measurements, BMI equals weight in pounds divided by height in inches squared, multiplied by 703.
What BMI is considered a healthy weight for adults?+
For adults age 20 and older, a BMI from 18.5 to less than 25 is categorized as healthy weight. BMI is still only a screening measure and should be considered with other health information.
Is BMI accurate for muscular people?+
BMI does not distinguish muscle from body fat. A muscular person can have a higher BMI even when body-fat levels are not high. Waist measurement, body composition, medical history, and clinical assessment may provide additional context.
Should children use this adult BMI calculator?+
No. Children and teenagers age 2 through 19 are evaluated using BMI percentiles that account for age and sex. This calculator is intended for adults age 20 and older.
Does BMI change with age?+
The standard adult category thresholds do not change by age, but body composition and health context can change substantially. Older adults may lose muscle or height, which can affect how useful BMI is for an individual.
Does this calculator save my height or weight?+
No account or server-side saving is built into this page. The calculation runs in the browser during the current session.
Health disclaimer: This adult BMI calculator provides a general screening estimate for informational and educational purposes. It does not diagnose a condition, directly measure body fat, or replace advice from a qualified healthcare professional. Seek professional guidance when weight changes are unexplained, rapid, related to illness, pregnancy, medication, eating concerns, or another health condition.