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Free BMI Calculator - Fast Browser Tool

Calculate adult body mass index using metric or imperial units. Review your BMI category, healthy-weight reference range, BMI Prime, and important interpretation limitations.

Calculate BMI See how it works
Metric and imperial units Adult categories Healthy-weight range No data uploads

Adult BMI Calculator

Enter your height and weight. Values are calculated locally and are not submitted or stored.

Intended for adults aged 20+

Your measurements

Choose a unit system and enter your current height and weight.

cm

kg

Private browser calculation. Your measurements are not uploaded, stored, or added to the URL.

Healthy range

This result falls within the commonly used adult BMI reference range of 18.5 through 24.9.

BMI category Healthy range
Healthy-weight range 53.5–72.0 kg
BMI Prime 0.97
Height used 170.0 cm
Weight used 70.0 kg
Range position Within reference range

Adult BMI category scale

Visual scale shown from BMI 10 to 50
Underweight
Healthy range
Overweight
Obesity I
Obesity II
Obesity III
BMI is a screening measure, not a diagnosis. It does not directly measure body fat, muscle mass, fitness, or overall health.
01
Private calculation Measurements remain in your browser
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Exact unit conversion Metric and imperial results agree
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Adult categories Clear category and reference range
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Context included Important limitations remain visible
BMI explained

A simple screening measure based on height and weight

Body mass index relates an adult's weight to the square of their height. It is widely used as a quick population-level screening measure because it requires only two measurements.

BMI categories can provide a useful starting point for a health discussion, but they do not directly measure body fat, muscle, bone density, fitness, nutrition, or fat distribution.

BMI should be interpreted in context

Muscular individuals may have a higher BMI without having high body fat. Older adults may have different body composition at the same BMI, and health risks can vary between individuals and populations.

Adult and child BMI are interpreted differently

The categories used here are intended for adults aged 20 and older. Children and teenagers require age- and sex-specific BMI percentiles interpreted with pediatric growth charts.

Clear and useful results

Everything needed for an adult BMI estimate

Switch units, understand the calculation, and review the result without unnecessary personal information.

kg

Metric measurements

Calculate BMI using kilograms and centimeters with decimal support.

lb

Imperial measurements

Use pounds, feet, and inches with exact conversion internally.

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Automatic unit switching

Change systems without losing the physical measurements already entered.

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BMI Prime

Compare your BMI with 25 using the simple BMI Prime ratio.

⌁

Category visualization

See the result positioned across the standard adult BMI categories.

ⓘ

Responsible guidance

Keep important limitations and appropriate-use information visible.

Three simple steps

How to calculate adult BMI

Get a clear screening estimate with only your height and weight.

01
Step 1

Choose your units

Select metric for centimeters and kilograms or imperial for feet, inches, and pounds.

02
Step 2

Enter height and weight

Use current, accurate measurements and check that the units match your selection.

03
Step 3

Interpret with context

Review the category and range while remembering that BMI is only one screening measure.

Adult category reference

Commonly used adult BMI categories

These thresholds are general adult screening references and do not represent an individual diagnosis.

Adult category BMI range General screening interpretation
Underweight Below 18.5 Below the commonly used adult reference range
Healthy range 18.5–24.9 Within the commonly used adult reference range
Overweight 25.0–29.9 Above the healthy adult reference range
Obesity Class I 30.0–34.9 First adult obesity screening category
Obesity Class II 35.0–39.9 Second adult obesity screening category
Obesity Class III 40.0 or higher Third adult obesity screening category
BMI has important limitations. Standard adult categories may require additional interpretation for highly muscular people, older adults, pregnancy, some ethnic populations, and people with specific medical conditions.
Better interpretation

Use BMI as one piece of a larger picture

Health cannot be summarized by a single height-and-weight ratio.

1

Use current measurements

Measure height without shoes and use a reliable scale under consistent conditions.

2

Consider body composition

Muscle mass, body-fat distribution, bone structure, and age can affect how BMI should be interpreted.

3

Look at long-term patterns

A single result offers less context than trends reviewed alongside other health information.

4

Discuss concerns professionally

A qualified healthcare professional can interpret BMI with medical history and other appropriate measures.

Common questions

BMI Calculator FAQ

What is BMI?

Body mass index, or BMI, is a screening measure that relates an adult's weight to the square of their height. It does not directly measure body fat or diagnose health.

How is BMI calculated?

Metric BMI is weight in kilograms divided by height in metres squared. For imperial values, pounds and total inches are converted to kilograms and metres before applying the same formula.

What is considered a healthy adult BMI?

The commonly used adult reference range is 18.5 through 24.9. BMI below 18.5 is categorized as underweight, while BMI of 25 or higher is divided into overweight and obesity categories.

Is BMI an accurate measure of body fat?

No. BMI does not directly distinguish fat, muscle, bone, or body-fat distribution. Muscular people and individuals with different body compositions can have similar BMI values.

Can this calculator be used for children or teenagers?

No. Children and teenagers require age- and sex-specific BMI percentiles interpreted with pediatric growth charts. This calculator uses adult categories intended for people aged 20 and older.

Should BMI be used during pregnancy?

Standard adult BMI categories are not designed to evaluate weight changes during pregnancy. Pregnancy-related weight and health questions should be discussed with a qualified healthcare professional.

Is this BMI result medical advice?

No. The result is an educational screening estimate and not a diagnosis or personalized medical recommendation. A healthcare professional can interpret BMI alongside medical history, body composition, and other health measures.

Continue calculating

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Calculate your adult BMI in seconds

Enter height and weight, switch between metric and imperial units, and review the result with the context it needs.

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