AZCalculate logo

Health

BMI Calculator

Use this BMI calculator to estimate adult body mass index from height and weight. Choose metric or imperial units, enter your measurements, and review the standard adult BMI category with clear notes about when BMI is useful and when it is limited.

bmibody mass indexhealthweightheightfitness

Calculator

Calculate instantly

BMI = weight (kg) / height (m)^2
Metric and imperial values are first converted to kilograms and meters, then weight is divided by height squared.
  1. The formula uses metric units, even when the original inputs are imperial.
  2. Height is squared so weight can be compared consistently across different heights.
  3. The result is compared with broad adult reference thresholds.

Inputs

Height and weight inputs

Choose a unit system, enter height and weight, and see a standard adult BMI screening reference with a clear visual explanation.

Breakdown

Clear result breakdown

Review the values that explain the primary result.

Underweight

below 18.5

Normal weight

18.5 to 24.9

Your current reference band

Overweight

25 to 29.9

Obesity range

30 or higher

Visual comparison

BMI reference comparison

Your BMI is shown alongside the standard adult reference thresholds. BMI is a screening measure, not a diagnosis.

Your BMI is shown alongside the standard adult reference thresholds. BMI is a screening measure, not a diagnosis.

Practical guidance

Insights for this scenario

A screening value, not a diagnosis

BMI is one broad weight-for-height screening measure. It does not directly measure body composition, fitness, or individual health.

Use context

Age, muscle mass, pregnancy, ethnicity, medical history, and clinical measurements can affect how a BMI value should be interpreted.

Ask when it matters

For a personal health concern, talk to a qualified healthcare professional rather than relying on one calculator result.

Visual reference

Your BMI falls in the Normal weight range

Normal weight - 18.5 to 24.9

This is the standard reference range commonly used for adult BMI screening.

Step-by-step solution

Follow the calculation path from known values to final result.

  1. 1

    Standardise the measurements

    Imperial values convert to kg and m

    72 kg and 1.75 m

    The formula uses metric units, even when the original inputs are imperial.

  2. 2

    Square the height

    height squared = H x H

    1.75 x 1.75

    Height is squared so weight can be compared consistently across different heights.

  3. 3

    Divide weight by height squared

    BMI = W / H^2

    72 / 3.063

    The result is compared with broad adult reference thresholds.

    23.5 - Normal weight

Formula explorer

BMI = weight (kg) / height (m)^2

Metric and imperial values are first converted to kilograms and meters, then weight is divided by height squared.

W(kg)
Weight: Body weight converted to kilograms.
H(m)
Height: Height converted to meters.

Assumptions and references

Units

  • kg
  • cm

Assumptions

  • This uses the standard adult BMI screening formula.
  • The input measurements are accurate and current.

Limitations

  • BMI is not a medical diagnosis or direct body-fat measurement.
  • Children, teenagers, pregnancy, athletic body composition, and health conditions need specialised assessment.

Worked examples

Easy

Metric BMI example

Known values

  • Weight: 72 kg
  • Height: 175 cm

Calculation

  • 1. Convert 175 cm to 1.75 m.
  • 2. Square 1.75 m.
  • 3. Divide 72 by 1.75 squared.

Result and meaning

BMI is about 23.5, within the standard adult reference range.

Real-world

Use the result with health context

Known values

  • A BMI result
  • Personal medical or fitness context

Calculation

  • 1. Treat the category as a starting screening point.
  • 2. Consider body composition and health history.
  • 3. Discuss meaningful concerns with a professional.

Result and meaning

A single BMI value is most useful as one input in a wider health conversation.

Learning guide

Understand the calculation

Concepts

  • BMI is a weight-for-height screening measure.
  • The same formula works worldwide after unit conversion.
  • A category describes a reference range, not a personal diagnosis.

Tips

  • Use accurate, current measurements.
  • Track change over time rather than fixating on a single result.
  • Use professional advice for personal health decisions.

Common mistakes

  • Using centimetres in the formula without converting to metres.
  • Treating BMI as a direct body-fat percentage.
  • Using adult thresholds for children or teenagers.

Educational notes

  • This calculator provides an estimate only and is not medical advice.

Glossary

Weight
Body weight normalized to kilograms.
Height
Height normalized to meters before squaring.

Related articles

Trust panel

Calculator quality and review

Reviewed by
AZCalculate health calculator review
Review date
2026-06-25
References
2
Trust score
91/100
Formula verified
Yes
Risk level
high
Category
Health
Calculator version
2.1
Formula version
2.1

Sign in to save this calculation and access it later.

Sign inCreate account

Trust note

Important estimate

BMI is a general adult screening measure only. BMI alone cannot diagnose health, and individual assessment requires qualified professional advice. Children and teenagers require age- and sex-specific assessment, and pregnancy or unusual muscle mass can make standard adult BMI less useful.

High risk contextDifficulty: easyConfidence estimate: 91/100Reviewed 2026-06-25Reviewed by: AZCalculate health calculator reviewCalculator v2.1 / Formula v2.12 sources listed

Formula and Explanation

BMI = weight (kg) / height (m)^2

The calculator converts height and weight into kilograms and meters, applies the standard adult BMI formula, rounds the result to one decimal place, and compares it with common adult reference categories.

Variable descriptions

W(kg)
Weight: Body weight normalized to kilograms.
H(m)
Height: Height normalized to meters before squaring.

Formula Notes

  • Metric inputs use kilograms and centimeters, with centimeters converted to meters.
  • Imperial inputs are converted to kilograms and meters before the formula is applied.
  • Adult BMI categories are screening references and are not a medical diagnosis.
  • Children, teenagers, pregnancy, and unusual muscle mass require more context than a standard adult BMI category.

Common uses

  • Check BMI
  • Compare wellness range
  • Track body metrics

Assumptions

What this calculation assumes

  • The calculator uses adult BMI reference categories.
  • Height and weight measurements are accurate and current.
  • The result is rounded to one decimal place for readability.

Avoid mistakes

Quick checks before you rely on the result

  • Using adult BMI categories for children or teenagers.
  • Treating BMI as a body-fat percentage.
  • Assuming BMI alone can diagnose health.
  • Ignoring pregnancy, high muscle mass, age, and body composition context.

Step-by-Step Explanation

Follow the reasoning, not only the final number.

  1. 1

    Set up the calculation

    Enter height and weight in metric or imperial units.

    Starting with clearly defined values and units prevents the most common calculation errors.

  2. 2

    Work through step 2

    Convert the measurements to kilograms and meters.

    This step transforms the known values into the form required by the formula.

  3. 3

    Work through step 3

    Square the height in meters.

    This step transforms the known values into the form required by the formula.

  4. 4

    Work through step 4

    Divide weight by height squared.

    This step transforms the known values into the form required by the formula.

  5. 5

    Interpret the result

    Compare the result with standard adult BMI categories.

    Compare the result with your real-world goal, such as check bmi.

Worked example

Adult BMI example

Known values

  • Weight: 72 kg
  • Height: 175 cm

Calculation

  1. 1. Convert 175 cm to 1.75 m.
  2. 2. Square 1.75 m to get 3.0625.
  3. 3. Divide 72 by 3.0625.

Result and meaning

BMI is about 23.5, which falls in the standard adult normal-weight reference range.

Calculator guide

About this BMI Calculator

Calculate body mass index using metric or imperial units and view the standard BMI category. This page includes an interactive calculator, concise formula notes, worked examples, FAQs, related calculators, and practical guidance you can revisit whenever needed.

bmibody mass indexhealthweightheightfitness

References

Sources used for this calculator

Found something that does not look right?

We work hard to keep every calculator accurate and useful. If you notice a calculation error, missing option, or unclear explanation, please let us know so we can review and correct it promptly.

Report an Issue

Calculator usage

Usage information loads after the calculator is ready.

FAQ

BMI Calculator FAQs

Is BMI a medical diagnosis?+

No. BMI is a screening estimate and should not replace guidance from a medical professional.

Does BMI work for athletes?+

BMI can overestimate body fat for muscular people because it does not distinguish muscle from fat mass.

What does BMI measure?+

BMI compares body weight with height using a standard adult screening formula. It does not directly measure body fat or health status.

How do I calculate BMI in metric units?+

Convert height to meters, square the height, then divide weight in kilograms by height squared.

How do I calculate BMI in imperial units?+

The calculator converts pounds, feet, and inches to kilograms and meters before applying the same BMI formula.

What BMI categories are shown?+

The adult reference categories are underweight below 18.5, normal weight from 18.5 to 24.9, overweight from 25 to 29.9, and obesity range at 30 or higher.

Is BMI a diagnosis?+

No. BMI is a general screening estimate and cannot diagnose health, disease, body fat percentage, or fitness.

Why can BMI be less useful for athletes?+

BMI does not separate muscle from fat, so people with high muscle mass can receive a higher BMI even when body composition differs from the average population.

Should children or teenagers use adult BMI categories?+

No. Children and teenagers need age- and sex-specific BMI assessment from pediatric growth references or qualified guidance.

Can pregnancy affect BMI interpretation?+

Yes. Standard adult BMI categories are not designed to interpret pregnancy-related body changes.

What should I do with my BMI result?+

Use it as one screening clue. For personal health concerns, discuss the result with a qualified healthcare professional.

Related tools

Related Calculators

Continue with closely related tools selected from the same subject and matching calculation needs.

Health

Body Fat Calculator

Estimate body fat percentage using waist, neck, height, and hip measurements.

Health

Calorie Calculator

Estimate daily calories from BMR, activity factor, and goal adjustment.

Health

Health Calculator

Estimate adult BMI, baseline energy needs, and a broad daily calorie planning target from height, weight, age, and activity.

PopularTrending
Explore all Health calculators
BMI Calculator - Body Mass Index and Adult BMI Category | AZCalculate