How to create a BMI calculator with JavaScript

Web Coding
Nov 12, 2020
1 min read

Today I will be teaching you how to create a BMI Calculator using only HTML, CSS and JavaScript.

HTML

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>Document</title>
</head>
<body>
 <!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>Document</title>
 <link rel="stylesheet" href="style.css">
</head>
<body>
 <div id="BMICalc">
 <h2>BMI Calculator</h2>
 <div class="row"> <p class="column">Height (cm): </p> <input type="number" class="column1" id="height"></div>
 <div class="row"> <p class="column">Weight (kg):</p> <input type="number" class="column1" id="weight"></div>
 <div class="row"> <button id="calculate">Calculate BMI</button> </div>
 <div class="row"><p id="BMI" class="column">BMI:</p> <span id="result" class="column1"></span> </div>
 </div>
 <script src="script.js"></script>
</body>

</html>
</body>
</html>

CSS

*{
 padding: 0;
 margin: 0;
}

body{
 min-height: 100vh;
 display: flex;
 align-items: center;
 justify-content: center;
 background-color: #19181A;
}

#BMICalc{
 background-color: #A16E83;
 border: 1px solid black;
 min-height: 20vh;
 width: 50%;
 border-radius: 25px;
 font-size: 16px;
}

h2{
 padding-top: 3vh;
 text-align: center;
 padding-bottom: 1vh;
}

#calc p{
 text-align: end;
}

.row {
 display: flex;
 flex-direction: row;
 justify-content: center;
  }
 

.column {
 flex-basis: 25%;
 margin-right: 1%;
}

.column1 {
 flex-basis: 45%;
 margin-left: 1%;
}

#Calculate{
 margin-top: 5px;
}

JavaScript

let height = document.getElementById('height');
let weight = document.getElementById('weight');
let calcBtn = document.getElementById('calculate');
let resultDisplay = document.getElementById('result');

calcBtn.addEventListener('click', calculateBMI);

function calculateBMI(){
 let BMI = ((weight.value / height.value / height.value)
    * 10000).toFixed(2);
 if (BMI < 18.5){
 resultDisplay.innerHTML = BMI + " you are considered underweight";
    } else if (BMI >= 18.5 && BMI < 25 ){
 resultDisplay.innerHTML = BMI + " you are considered normal weight";
    } else if (BMI >= 25 && BMI<30){
 resultDisplay.innerHTML = BMI + " you are considered overweight";
    } else {
 resultDisplay.innerHTML = BMI + " you are considered obese";
    }
}

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