Calzivo

Health & Fitness Calculators

BMI Calculator

Calculate adult BMI from height and weight with cautious screening-category context.

Calculate adult BMI

For adults age 20 and older. Choose one unit system and enter height and weight.

Select units and enter measurements, then calculate.

Formula and exact unit conversion

Metric BMI is weight in kilograms divided by squared height in metres. US inputs use exactly 1 pound = 0.45359237 kilograms and 1 inch = 2.54 centimetres before the same metric formula is applied.

Example: 70 / (1.75 x 1.75) = 22.857142857..., displayed as 22.9.

Adult screening interpretation

  • Underweight: below 18.5
  • Healthy weight: 18.5 to below 25
  • Overweight: 25 to below 30
  • Obesity: 30 or above

These are CDC adult screening categories, not diagnoses or individual health conclusions.

BMI and body composition

BMI does not distinguish fat, muscle, bone, or fat distribution. For separate circumference-based context, see the Body Fat Calculator.

Limitations and common mistakes

  • Do not use adult categories for children or teenagers.
  • Do not classify from the rounded display value.
  • Do not treat BMI as measured body fat or a diagnosis.
  • Pregnancy, body composition, and individual health context can change interpretation.

Quick answers

What this calculator answers

  • Result: Calculates BMI to one decimal and classifies the raw value using CDC adult screening categories.
  • Audience: The category interpretation is for adults age 20 and older.
  • Units: US measurements are converted exactly to kilograms and centimetres before calculation.
  • Limit: BMI does not directly measure body fat, muscle, or individual health.

Transparency note

Accuracy and limitations

Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.

Health and fitness results are estimates, not medical advice. Formulas simplify real bodies and cycles, so important health decisions should be checked with a qualified clinician.

Reference check

Sources and references

These references provide background context for the topic. They do not replace official advice or documents for personal decisions.

How to Use This Tool

Use these steps to enter the right inputs and interpret the result correctly.

1

Enter the required values in the input fields.

2

The tool will automatically calculate or process the data.

3

Review the results in the result area.

4

Copy or reset the results as needed.

Related Tools

Compare BMI with body-composition, resting-energy, calorie, and macro tools.

Body Fat Calculator

Estimate body fat percentage from defined circumference measurements with a historical equation.

Check Body Fat

BMR Calculator

Estimate resting energy with the Mifflin-St Jeor equation and transparent assumptions.

Calculate BMR

Calorie Calculator

Estimate a maintenance-energy range from resting energy and a disclosed activity band.

Calculate Calories

Macro Calculator

Convert entered calories and macro percentages into protein, carbohydrate, and fat grams.

Calculate Macros

Related Guides

Background reading and explanations related to BMI Calculator.

BMI Limits: What BMI Can and Cannot Tell You

Understand BMI as a screening estimate and where body composition context matters.

Read Guide

BMI Explained (What It Means and When It Misleads You)

What your BMI score really means.

Read Guide

Frequently Asked Questions

Common questions about BMI Calculator and how to read the result.

Why can a displayed 18.5 still be Underweight?

The category uses the unrounded BMI. A value just below 18.5 can display as 18.5 after one-decimal rounding while remaining below the raw boundary.

Does BMI measure body fat?

No. BMI compares weight with height and does not directly measure body composition.

Can this adult category be used for children?

No. CDC uses age- and sex-specific growth-chart interpretation for people younger than 20.

Does the US calculation use 703?

The calculator converts pounds and inches with exact constants instead of using a rounded 703 shortcut.