BMI Calculator

BMI Calculator

BMI Calculator

About This calculator

BMI, or Body Mass Index, is a numerical value of a person's weight in relation to their height. It is a commonly used method to assess whether an individual has a healthy body weight for a given height. BMI is a simple and quick screening tool that can provide an estimate of body fat and help identify potential health risks associated with being underweight, normal weight, overweight, or obese.

BMI categories are generally defined as follows:

  • Underweight: BMI less than 18.5
  • Normal weight: BMI between 18.5 and 24.9
  • Overweight: BMI between 25 and 29.9
  • Obesity: BMI 30 or greater

It's important to note that while BMI is a useful screening tool, it does not directly measure body fat percentage, distribution of fat, or other factors like muscle mass. Therefore, individuals with the same BMI may have different body compositions. For a more comprehensive health assessment, it's advisable to consult with a healthcare professional who can take into account various factors.

For Adults:

  • Underweight: BMI less than 18.5
  • Normal weight: BMI between 18.5 and 24.9
  • Overweight: BMI between 25 and 29.9
  • Obesity:
    • Class I: BMI between 30 and 34.9
    • Class II: BMI between 35 and 39.9
    • Class III: BMI 40 or greater

For Children:

BMI in children and adolescents is age and sex-specific, as the amount of body fat changes with age and differs between boys and girls. BMI percentiles are used to assess whether a child has a healthy weight. The categories generally include:

  • Underweight: Less than the 5th percentile
  • Normal weight: 5th to less than the 85th percentile
  • Overweight: 85th to less than the 95th percentile
  • Obesity: 95th percentile or greater

The BMI-for-age percentiles are usually plotted on growth charts specific to age and sex. It's important to consult with healthcare professionals, such as pediatricians, for a more accurate assessment and interpretation of BMI in children.

How To Use This Calculator ?

  1. Enter Height and Select Unit:
    • In the "Height" input field, enter your height in numerical value.
    • Select the corresponding unit (cm, m, in, or ft) from the dropdown next to the height input.
  2. Enter Weight and Select Unit:
    • In the "Weight" input field, enter your weight in numerical value.
    • Select the corresponding unit (kg or lbs) from the dropdown next to the weight input.
  3. Select Criteria:
    • Choose the appropriate criteria from the "Select Criteria" dropdown. You can choose between "Adult" and "Child."
  4. Click "Calculate BMI":
    • Click the "Calculate BMI" button after entering your height, weight, and criteria.
  5. View Results:
    • The calculated BMI and its interpretation based on the selected criteria will be displayed in the result area below the button.
  6. Interpretation:
    • The result provides information about your BMI category, such as "Underweight," "Normal weight," "Overweight," or "Obesity."

Examples To Try

  1. Example for an Adult:
    • Height: 175 cm
    • Weight: 70 kg
  2. Example for a Child:
    • Height: 130 cm
    • Weight: 30 kg
  3. Example for an Adult with Different Units:
    • Height: 5 ft 9 in
    • Weight: 150 lbs
  4. Example for a Child with Different Units:
    • Height: 4 ft 3 in
    • Weight: 80 lbs
  5. Example for an Underweight Adult:
    • Height: 160 cm
    • Weight: 45 kg
  6. Example for an Underweight Child:
    • Height: 120 cm
    • Weight: 20 kg
  7. Example for a Normal Weight Adult:
    • Height: 180 cm
    • Weight: 70 kg
  8. Example for a Normal Weight Child:
    • Height: 140 cm
    • Weight: 35 kg
  9. Example for an Overweight Adult:
    • Height: 165 cm
    • Weight: 80 kg
  10. Example for an Overweight Child:
    • Height: 125 cm
    • Weight: 45 kg
  11. Example for an Obese Adult:
    • Height: 170 cm
    • Weight: 100 kg
  12. Example for an Obese Child:
    • Height: 150 cm
    • Weight: 60 kg
  13. Example with Imperial Units (Feet and Pounds):
    • Height: 6 ft 2 in
    • Weight: 180 lbs
  14. Example with Mixed Units (Centimeters and Pounds):
    • Height: 160 cm
    • Weight: 120 lbs
  15. Example with Mixed Units (Meters and Pounds):
    • Height: 1.75 m
    • Weight: 150 lbs

How This Calculator Function ?

  1. HTML Structure:
    • The HTML document includes input fields for height and weight, dropdowns for unit selection (cm, m, in, ft, kg, lbs), a dropdown for criteria selection (adult or child), a "Calculate BMI" button, and a result area to display the calculated BMI.
  2. JavaScript Functions:
    • The JavaScript code includes functions to perform the BMI calculation and interpretation.
  3. calculateBMI Function:
    • This function is triggered when the user clicks the "Calculate BMI" button.
    • It retrieves the user-inputted values for height, weight, height unit, weight unit, and criteria.
    • It converts the height to meters and weight to kilograms based on the selected units.
    • It calculates the BMI using the standard formula: ���=Weight in kilograms(Height in meters)2BMI=(Height in meters)2Weight in kilograms​
    • It then calls either the interpretBMI or interpretChildBMI function based on the selected criteria.
  4. interpretBMI Function:
    • This function interprets the BMI result for adults.
    • It compares the calculated BMI against predefined ranges to determine the weight status category (underweight, normal weight, overweight, or obesity).
    • It generates a result message with the BMI value and the corresponding weight status category.
  5. interpretChildBMI Function:
    • This function interprets the BMI result for children.
    • It uses BMI percentiles to determine the weight status category for children.
    • It generates a result message with the BMI value and the corresponding weight status category.
  6. Updating the Result:
    • The result message is then displayed in the HTML result area.
  7. Styling:
    • The HTML and CSS include styling to improve the visual presentation of the calculator, providing a user-friendly and responsive design.

Where This Calculator Can Be Used ?

  1. Healthcare Settings:
    • Doctors, nurses, and other healthcare professionals can use BMI calculations as part of routine health assessments to screen for potential weight-related health issues.
  2. Fitness and Nutrition:
    • Personal trainers and nutritionists may use BMI as an initial screening tool to assess a client's overall health and make informed decisions about exercise and dietary recommendations.
  3. Wellness Programs:
    • Employers offering wellness programs may use BMI assessments as part of health and fitness initiatives to encourage employees to maintain a healthy lifestyle.
  4. Schools and Educational Institutions:
    • School nurses and physical education teachers might use BMI measurements to monitor the health and well-being of students and identify potential concerns.
  5. Research Studies:
    • Researchers studying population health, obesity, and related conditions may use BMI calculations to analyze trends and patterns in different demographic groups.
  6. Weight Management Programs:
    • Individuals participating in weight management programs or weight loss clinics can use the BMI calculator to track their progress and set realistic goals.
  7. Public Health Campaigns:
    • Public health organizations may incorporate BMI assessments in awareness campaigns to promote healthy lifestyle choices and prevent obesity-related health issues.
  8. Online Health Platforms:
    • Various health and fitness websites or mobile apps may integrate BMI calculators as a feature to provide users with a quick estimate of their body weight status.
  9. Preventive Health Screenings:
    • BMI calculations can be part of routine health screenings or check-ups to identify individuals at risk of obesity-related conditions like diabetes, heart disease, or hypertension.
  10. Fitness Apps and Wearables:
    • Mobile applications and wearable fitness devices often include BMI calculators to offer users insights into their overall health and fitness levels.
<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>BMI Calculator</title>
    <link rel="stylesheet" href="style.css">

<div class="calculator-container">
    <h2>BMI Calculator</h2>
    <label for="height">Height:</label>
    <input type="number" id="height" placeholder="Enter height">
    <select id="heightUnit">
        <option value="cm">cm</option>
        <option value="m">m</option>
        <option value="in">in</option>
        <option value="ft">ft</option>

    <label for="weight">Weight:</label>
    <input type="number" id="weight" placeholder="Enter weight">
    <select id="weightUnit">
        <option value="kg">kg</option>
        <option value="lbs">lbs</option>

    <label for="criteria">Select Criteria:</label>
    <select id="criteria">
        <option value="adult">Adult</option>
        <option value="child">Child</option>

    <button onclick="calculateBMI()">Calculate BMI</button>

    <div id="result"></div>

<script src="script.js"></script>
  1. <!DOCTYPE html>: This declaration defines the document type and version of HTML used.
  2. <html lang="en">: The root element of the HTML document with the language attribute set to "en" (English).
  3. <head>: Contains metadata about the HTML document, such as character set, viewport settings, and the title of the page.
  4. <meta charset="UTF-8">: Sets the character encoding to UTF-8.
  5. <meta name="viewport" content="width=device-width, initial-scale=1.0">: Specifies the viewport settings for responsive design.
  6. <title>BMI Calculator</title>: Sets the title of the HTML document.
  7. <style>: Contains the CSS styles for styling the BMI calculator.
body {
    font-family: Arial, sans-serif;
    margin: 20px;
    background-color: #f4f4f4;

.calculator-container {
    max-width: 500px;
    margin: auto;
    padding: 20px;
    border: 1px solid #ccc;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    background-color: #fff;
    transition: box-shadow 0.3s ease-in-out;

.calculator-container:hover {
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.2);

h2 {
    text-align: center;
    color: #333;

label {
    display: block;
    margin-bottom: 8px;
    color: #555;

input, select {
    width: 40%;
    padding: 10px;
    margin-bottom: 16px;
    box-sizing: border-box;
    border: 1px solid #ccc;
    border-radius: 4px;
    transition: border-color 0.3s ease-in-out;

input:focus, select:focus {
    border-color: #4CAF50;

button {
    background-color: #4CAF50;
    color: white;
    padding: 12px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.3s ease-in-out;

button:hover {
    background-color: #45a049;

#result {
    margin-top: 20px;
    text-align: center;
    font-weight: bold;
    color: #333;

The CSS styles define the layout and appearance of the BMI calculator. Key styles include:

  • Setting the body font, margin, and background color.
  • Styling the calculator container with a border, border-radius, box-shadow, and transition effects.
  • Styling form elements like input, select, and button with specified widths, padding, and transitions.
  • Applying hover effects to the calculator container and the calculate button.
  • Defining styles for the result display.

Body Section:

  1. <body>: The main content of the HTML document.
  2. <div class="calculator-container">: A container for the BMI calculator with a form inside.
  3. Heading, labels, input fields, and dropdowns for entering height, weight, and selecting criteria (adult or child).
  4. <button onclick="calculateBMI()">Calculate BMI</button>: A button triggering the calculateBMI function when clicked.
  5. <div id="result"></div>: An empty div element to display the calculated BMI result.
function calculateBMI() {
    const height = parseFloat(document.getElementById("height").value);
    const weight = parseFloat(document.getElementById("weight").value);
    const heightUnit = document.getElementById("heightUnit").value;
    const weightUnit = document.getElementById("weightUnit").value;
    const criteria = document.getElementById("criteria").value;

    // Convert height and weight to standard units (meters and kilograms)
    const heightInMeters = (heightUnit === "cm") ? height / 100 : height * 0.3048;
    const weightInKg = (weightUnit === "lbs") ? weight * 0.453592 : weight;

    // Calculate BMI
    const bmi = weightInKg / (heightInMeters * heightInMeters);

    // Display result based on criteria
    let resultMessage;
    if (criteria === "adult") {
        resultMessage = interpretBMI(bmi);
    } else {
        resultMessage = interpretChildBMI(bmi);

    document.getElementById("result").innerHTML = resultMessage;

function interpretBMI(bmi) {
    if (bmi < 18.5) {
        return `BMI: ${bmi.toFixed(2)} - Underweight`;
    } else if (bmi >= 18.5 && bmi < 25) {
        return `BMI: ${bmi.toFixed(2)} - Normal weight`;
    } else if (bmi >= 25 && bmi < 30) {
        return `BMI: ${bmi.toFixed(2)} - Overweight`;
    } else {
        return `BMI: ${bmi.toFixed(2)} - Obesity`;

function interpretChildBMI(bmi) {
    if (bmi < 5) {
        return `BMI: ${bmi.toFixed(2)} - Underweight`;
    } else if (bmi >= 5 && bmi < 85) {
        return `BMI: ${bmi.toFixed(2)} - Normal weight`;
    } else if (bmi >= 85 && bmi < 95) {
        return `BMI: ${bmi.toFixed(2)} - Overweight`;
    } else {
        return `BMI: ${bmi.toFixed(2)} - Obesity`;

The <script> tag contains JavaScript code for calculating and interpreting BMI.

  • calculateBMI(): Retrieves input values, converts units to standard units (meters and kilograms), calculates BMI, and displays the result based on selected criteria (adult or child).
  • interpretBMI(bmi): Returns a message based on the calculated BMI for adults.
  • interpretChildBMI(bmi): Returns a message based on the calculated BMI for children.

How it Works:

  1. User inputs height, weight, and selects criteria (adult or child).
  2. Clicking "Calculate BMI" triggers the calculateBMI function.
  3. The function converts height and weight to standard units, calculates BMI, and interprets the result based on the selected criteria.
  4. The result is displayed in the <div id="result"></div> element.

This BMI calculator is designed to provide different interpretations of BMI for adults and children. The styling enhances the user interface by providing a visually appealing and responsive design.

How To Implement

Implementing this Confidence Interval Calculator on WordPress involves a few steps. Here's a step-by-step guide:

1. Access WordPress Admin Dashboard

Log in to your WordPress admin dashboard.

2. Create a New Page

Navigate to Pages > Add New in the WordPress admin.

Give your page a title, such as "Confidence Interval Calculator."

3. Switch to HTML Editor

On the page editor, switch to the HTML editor. Look for a tab that says "HTML" or "Code."

4. Copy HTML Code

Copy the entire HTML code (from <!DOCTYPE html> to the closing </html>) from your index.html file.

5. Paste HTML Code

Paste the copied HTML code into the HTML editor of your WordPress page.

6. Add CSS

Copy the entire CSS code (from the <style> tag in the styles.css file) and paste it into the WordPress page's HTML editor, preferably within the <head> section.

7. Add JavaScript

Copy the entire JavaScript code (from the <script> tag in the script.js file) and paste it into the WordPress page's HTML editor, preferably just before the closing </body> tag.

8. Save and Publish

Save the changes to your WordPress page.

Click the "Publish" button to make the page live.

9. View Your Page

Visit the page on your WordPress site to see the Confidence Interval Calculator in action.

Additional Considerations:

  • WordPress Theme Compatibility: Ensure that your WordPress theme supports the custom styles and scripts you've added. If needed, you may have to adjust styles to fit seamlessly with your theme.
  • Plugin Usage: If you find that directly pasting HTML, CSS, and JavaScript into the page editor is causing issues, consider using a plugin like "Insert Headers and Footers" to add your custom code.
  • Responsive Design: Check if the calculator layout is responsive. If not, you might need to make adjustments to the CSS for better responsiveness.
  • Debugging: If something doesn't work as expected, use the browser's developer tools (usually accessible by right-clicking on the page and selecting "Inspect" or "Inspect Element") to check for errors in the console tab.

By following these steps, you should be able to implement the Confidence Interval Calculator on your WordPress site. Remember to test the calculator thoroughly to ensure it functions correctly within the WordPress environment.


  1. What is BMI?
    • BMI stands for Body Mass Index. It is a numerical value of a person's weight in relation to their height.
  2. How is BMI calculated?
    • BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters.
  3. What units are commonly used for BMI calculations?
    • Common units for BMI calculations include kilograms and meters, as well as pounds and inches. The choice depends on regional preferences.
  4. What does a high BMI indicate?
    • A high BMI may indicate excess body weight, but it does not directly measure body fat. Further assessments are needed to determine overall health.
  5. What does a low BMI indicate?
    • A low BMI may indicate underweight, which can also pose health risks. Again, additional assessments are necessary for a comprehensive evaluation.
  6. What are the general BMI categories for adults?
    • The general BMI categories for adults are underweight (BMI < 18.5), normal weight (BMI 18.5–24.9), overweight (BMI 25–29.9), and obesity (BMI ≥ 30).
  7. What BMI range is considered healthy for adults?
    • A BMI between 18.5 and 24.9 is generally considered a healthy weight range for adults.
  8. How does BMI differ for children and adolescents?
    • BMI for children and adolescents is assessed using percentiles based on age and sex due to growth and development variations.
  9. What does a BMI percentile for a child indicate?
    • A BMI percentile for a child indicates their position relative to others of the same age and sex. For example, a BMI at the 75th percentile means the child has a higher BMI than 75% of their peers.
  10. Is BMI an accurate measure of body fat percentage?
    • No, BMI is not an accurate measure of body fat percentage. It provides a general estimation based on weight and height.
  11. What are the limitations of BMI?
    • BMI has limitations as it does not consider factors like muscle mass, body composition, or distribution of fat.
  12. Can athletes with higher muscle mass have a misleading BMI?
    • Yes, athletes with higher muscle mass may have a higher BMI, which can be misleading as muscle weighs more than fat.
  13. Why might BMI interpretation differ for adults and children?
    • BMI interpretation differs because children's body composition changes with age, and their growth patterns vary.
  14. When should BMI be used as a health assessment tool?
    • BMI should be used as a screening tool for assessing potential weight-related health issues, but a comprehensive evaluation is needed for accurate health assessments.
  15. Can BMI be used as the sole indicator of health?
    • No, BMI should not be used as the sole indicator of health. Other factors such as lifestyle, diet, and medical history should be considered.
  16. How often should BMI be calculated?
    • BMI can be calculated periodically as part of routine health assessments, but it doesn't need to be calculated daily. Frequency depends on individual health needs.
  17. What role does BMI play in weight management programs?
    • BMI can be used in weight management programs to set initial goals and track progress, but it is not the only factor considered.
  18. How can someone interpret their BMI result?
    • Individuals can interpret their BMI result by comparing it to established categories (underweight, normal weight, overweight, obesity) and seeking further guidance from healthcare professionals.
  19. Is BMI used internationally?
    • Yes, BMI is used internationally, and different countries may have specific guidelines for interpretation.
  20. What should someone do if their BMI falls outside the normal range?
    • If someone's BMI falls outside the normal range, it's advisable to consult with a healthcare professional for a thorough health assessment and personalized guidance.