BMI & Healthy Weight Range Calculator

Calculate BMI for adults, children, and teens in U.S. or metric units. See BMI categories, healthy weight range, percentiles, charts, and formulas.

Adjust your measurements to update your BMI instantly

Your BMI23.7Healthy weight

Adult interpretation: male adults use the same BMI formula and category thresholds.

Healthy BMI range18.5-24.9Adult screening range

Healthy weight for height128.9-174.2 lbBased on BMI 18.5-24.9

BMI Prime0.95BMI divided by 25

Ponderal Index13.3kg/m³

Where your BMI falls

UnderweightBelow 18.5

Healthy18.5 to 24.9

Overweight25.0 to 29.9

Obesity30.0 or higher

Adult BMI categories

Classification	BMI range
Underweight	Below 18.5
Healthy weight	18.5-24.9
Overweight	25-29.9
Obesity class 1	30-34.9
Obesity class 2	35-39.9
Obesity class 3	40 or higher

BMI is a screening measure, not a diagnosis. It does not directly measure body fat or account for muscle mass, pregnancy, or individual health conditions.

What does the BMI & Healthy Weight Range Calculator calculate?

The BMI & Healthy Weight Range Calculator converts the values you enter into a structured estimate using the formulas and assumptions documented on this page. Use the result to compare scenarios, review the calculation details, and identify sensitive inputs. Check the guide and formula sections before using the estimate for an important decision.

BMI and Healthy Weight Range at a Glance

Calculate BMI with U.S. customary or metric measurements.
Use fixed CDC categories for adults age 20 and older.
Use age- and sex-specific CDC BMI-for-age percentiles for ages 2-19.
See an adult healthy-weight screening range, BMI Prime, and Ponderal Index.
Treat the result as a screening estimate, not a diagnosis or body-fat measurement.

History of Body Mass Index

The height-to-weight relationship now called body mass index grew from nineteenth-century population research. The modern term BMI became common much later as researchers and public-health agencies adopted the ratio for screening and population comparisons.

Current U.S. guidance separates adult BMI categories from child and teen BMI-for-age interpretation. Adults use fixed thresholds. Growing children and teens are compared with age- and sex-specific CDC reference data.

What This BMI Calculator Does

The calculator divides weight in kilograms by height in meters squared. It accepts feet, inches, and pounds or centimeters and kilograms, normalizes the measurements, and classifies the unrounded result. Review the BMI Calculator assumptions before relying on this result for decisions.

For adults, it shows the CDC category and the weight range that corresponds to BMI 18.5 through the boundary at 25 for the entered height. For ages 2-19, it estimates a BMI-for-age percentile, category, and percent of the age- and sex-specific 95th-percentile BMI.

Who Should Use It

For “Who Should Use It,” the BMI Calculator organizes the relevant inputs, applies the documented method, and shows a result that can be compared across scenarios. The points below identify the specific considerations and assumptions users should review before relying on the estimate.

Adults who want a quick weight-for-height screening estimate.
Parents and caregivers preparing for a discussion about a child's growth.
Students learning the metric and U.S. BMI formulas.
People comparing how the same measurements appear in U.S. and metric units.

Pregnancy, athletic body composition, older age, medical conditions, and changes in growth can require more context than BMI alone provides.

Problems It Solves

Converts common height and weight units before calculating.
Prevents adult thresholds from being applied to children and teens.
Shows where a result falls instead of presenting a number without context.
Calculates an adult screening range for the entered height.
Uses the CDC extended method for very high pediatric percentiles.

Key Benefits

The tool keeps full calculation precision for classification, displays a readable rounded result, and uses one tested engine across the webpage, examples, widget, and PDF report. The adult and pediatric result views are intentionally different because they answer different screening questions.

BMI Definitions

BMI: Body mass index, calculated as kilograms divided by meters squared.
Adult category: A CDC screening band for adults age 20 and older: underweight, healthy weight, overweight, or an obesity class.
BMI-for-age percentile: A comparison with the CDC reference population for a child or teen of the same age and sex.
Percent of P95: The child's BMI divided by the age- and sex-specific 95th-percentile BMI, expressed as a percentage.
BMI Prime: Adult BMI divided by 25, the boundary where the adult overweight category begins.
Ponderal Index: A related weight-to-height measure that divides kilograms by meters cubed.

When to Use It

Use the calculator after taking current height and weight measurements, when reviewing a routine screening result, or before discussing weight or growth with a qualified healthcare professional. For children and teens, one result is most useful when considered with the pattern across earlier measurements.

How the Calculation Works

For “How the Calculation Works,” the BMI Calculator organizes the relevant inputs, applies the documented method, and shows a result that can be compared across scenarios. The points below identify the specific considerations and assumptions users should review before relying on the estimate.

Metric: BMI = weight in kg / height in m²

U.S. customary: BMI = 703 × weight in lb / height in in²

The entered measurements are validated and converted to metric units.
The engine calculates BMI without rounding the intermediate value.
Age determines whether adult or pediatric interpretation applies.
Adult results use fixed CDC cutoffs. Pediatric results use the entered age in months, sex, and CDC growth-chart parameters.
The interface rounds only the displayed values and highlights the category based on the unrounded result.

Read the complete BMI formulas and variable definitions or follow the step-by-step BMI guide.

Common BMI Calculator Mistakes

Mixing pounds with metric height or kilograms with feet and inches.
Entering total inches in the inches field instead of the remainder after feet.
Using an old, estimated, clothed, or shoe-on measurement.
Applying adult category cutoffs to a person younger than 20.
Treating BMI as a direct measure of body fat or a medical diagnosis.

Frequently Asked Questions

What is a healthy BMI?

For adults age 20 and older, the CDC healthy-weight category is a BMI from 18.5 to less than 25. Children and teens use BMI-for-age percentiles instead. Use realistic inputs and review the BMI Calculator assumptions before relying on this result for decisions.

Is BMI different for women and men?

No for adults: the formula and category cutoffs are the same. For ages 2-19, sex and exact age select the CDC BMI-for-age reference. For a useful BMI Calculator result, use realistic inputs, compare relevant scenarios, and review the stated assumptions before making a decision.

What BMI is overweight or obesity?

For adults, overweight begins at BMI 25 and obesity begins at BMI 30. Pediatric categories use sex- and age-specific percentiles. For a useful BMI Calculator result, use realistic inputs, compare relevant scenarios, and review the stated assumptions before making a decision.

How is child and teen BMI calculated?

The calculator first computes BMI from height and weight, then uses CDC sex-specific BMI-for-age reference data for the entered age in years and months. Use realistic inputs and review the BMI Calculator assumptions before relying on this result for decisions.

Does this calculator use the CDC extended BMI method?

Yes. It uses the CDC 2000 LMS method through the 95th percentile and the 2022 Extended BMI-for-age sigma method above the 95th percentile. For a useful BMI Calculator result, use realistic inputs, compare relevant scenarios, and review the stated assumptions before making a decision.

Is BMI accurate for athletes?

BMI does not distinguish muscle from body fat, so a muscular person can have a higher BMI without having high body fat. For a useful BMI Calculator result, use realistic inputs, compare relevant scenarios, and review the stated assumptions before making a decision.

Can BMI diagnose a health condition?

No. BMI is a screening measure and should be interpreted with health history, growth patterns, body composition, and other clinical information. For a useful BMI Calculator result, use realistic inputs, compare relevant scenarios, and review the stated assumptions before making a decision.

Can I use this BMI calculator during pregnancy?

Standard BMI categories do not account for pregnancy-related weight changes. Use individualized guidance from a prenatal healthcare professional. For a useful BMI Calculator result, enter realistic values, compare relevant scenarios, check the calculation details, and review the definitions, assumptions, and limitations before using the estimate for an important decision.

One Useful Fact

Adult sex does not change the BMI formula or CDC category cutoffs. Sex affects this calculator only for ages 2-19, where it selects the appropriate growth-chart reference.

Conclusion

BMI is a convenient starting point because it uses measurements most people can obtain easily. Its value comes from using the right interpretation for age and combining the result with health history, body composition, growth patterns, and professional judgment when needed.