function showShapeInputs() {
var shape = document.getElementById("shapeSelect").value;
document.getElementById("squareInputs").style.display = "none";
document.getElementById("rectangleInputs").style.display = "none";
document.getElementById("circleInputs").style.display = "none";
document.getElementById("triangleInputs").style.display = "none";
if (shape === "square") {
document.getElementById("squareInputs").style.display = "block";
} else if (shape === "rectangle") {
document.getElementById("rectangleInputs").style.display = "block";
} else if (shape === "circle") {
document.getElementById("circleInputs").style.display = "block";
} else if (shape === "triangle") {
document.getElementById("triangleInputs").style.display = "block";
}
document.getElementById("result").innerHTML = ""; // Clear previous result
}
function calculatePerimeter() {
var shape = document.getElementById("shapeSelect").value;
var perimeter = 0;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous result
if (shape === "square") {
var side = parseFloat(document.getElementById("squareSide").value);
if (isNaN(side) || side <= 0) {
resultDiv.innerHTML = "Please enter a valid positive number for the side length.";
return;
}
perimeter = 4 * side;
resultDiv.innerHTML = "The perimeter of the square is: " + perimeter.toFixed(2);
} else if (shape === "rectangle") {
var length = parseFloat(document.getElementById("rectangleLength").value);
var width = parseFloat(document.getElementById("rectangleWidth").value);
if (isNaN(length) || length <= 0 || isNaN(width) || width <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for length and width.";
return;
}
perimeter = 2 * (length + width);
resultDiv.innerHTML = "The perimeter of the rectangle is: " + perimeter.toFixed(2);
} else if (shape === "circle") {
var radius = parseFloat(document.getElementById("circleRadius").value);
if (isNaN(radius) || radius <= 0) {
resultDiv.innerHTML = "Please enter a valid positive number for the radius.";
return;
}
perimeter = 2 * Math.PI * radius;
resultDiv.innerHTML = "The circumference (perimeter) of the circle is: " + perimeter.toFixed(2);
} else if (shape === "triangle") {
var sideA = parseFloat(document.getElementById("triangleSideA").value);
var sideB = parseFloat(document.getElementById("triangleSideB").value);
var sideC = parseFloat(document.getElementById("triangleSideC").value);
if (isNaN(sideA) || sideA <= 0 || isNaN(sideB) || sideB <= 0 || isNaN(sideC) || sideC sideC) && (sideA + sideC > sideB) && (sideB + sideC > sideA))) {
resultDiv.innerHTML = "The entered side lengths do not form a valid triangle (Triangle Inequality Theorem).";
return;
}
perimeter = sideA + sideB + sideC;
resultDiv.innerHTML = "The perimeter of the triangle is: " + perimeter.toFixed(2);
}
}
// Initialize the display on page load
document.addEventListener('DOMContentLoaded', function() {
showShapeInputs();
});
.perimeter-calculator-container {
background-color: #f9f9f9;
border: 1px solid #ddd;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
font-family: Arial, sans-serif;
}
.perimeter-calculator-container h2 {
color: #333;
text-align: center;
margin-bottom: 20px;
}
.perimeter-calculator-container p {
margin-bottom: 15px;
line-height: 1.6;
}
.perimeter-calculator-container label {
display: block;
margin-bottom: 8px;
font-weight: bold;
color: #555;
}
.perimeter-calculator-container input[type="number"],
.perimeter-calculator-container select {
width: calc(100% – 22px);
padding: 10px;
margin-bottom: 15px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.perimeter-calculator-container button {
background-color: #007bff;
color: white;
padding: 12px 20px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
width: 100%;
box-sizing: border-box;
}
.perimeter-calculator-container button:hover {
background-color: #0056b3;
}
.perimeter-calculator-container #result {
margin-top: 20px;
padding: 10px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
color: #333;
}
.perimeter-calculator-container div[id$="Inputs"] {
margin-bottom: 15px;
padding: 10px;
border: 1px dashed #e0e0e0;
border-radius: 5px;
background-color: #fdfdfd;
}
Understanding Perimeter: The Boundary of Shapes
Perimeter is a fundamental concept in geometry that refers to the total distance around the outside of a two-dimensional shape. Imagine walking along the edge of a garden; the total distance you walk is its perimeter. It's a crucial measurement in various real-world applications, from fencing a yard to framing a picture or determining the length of trim needed for a room.
Why is Perimeter Important?
- Construction and Home Improvement: Builders and DIY enthusiasts use perimeter calculations to estimate materials like fencing, baseboards, crown molding, or even the amount of decorative lighting needed for a building's exterior.
- Gardening and Landscaping: Knowing the perimeter of a garden bed helps in planning borders, edging, or determining the length of irrigation pipes.
- Sports and Recreation: The perimeter defines the boundaries of sports fields (like a soccer pitch or a basketball court), ensuring fair play and consistent dimensions.
- Design and Art: Artists and designers might use perimeter to calculate the length of material needed for a frame or border around their work.
How to Calculate Perimeter for Common Shapes:
1. Square
A square is a quadrilateral with four equal sides and four right angles. To find its perimeter, you simply multiply the length of one side by four.
Formula: Perimeter = 4 × side
Example: If a square garden bed has a side length of 5 meters, its perimeter is 4 × 5 = 20 meters.
2. Rectangle
A rectangle is a quadrilateral with four right angles, where opposite sides are equal in length. Its perimeter is calculated by adding the lengths of all four sides, or more simply, by adding the length and width and then multiplying by two.
Formula: Perimeter = 2 × (length + width)
Example: A rectangular swimming pool is 10 meters long and 4 meters wide. Its perimeter is 2 × (10 + 4) = 2 × 14 = 28 meters.
3. Circle (Circumference)
For a circle, the perimeter is called the circumference. It's the distance around the circle. This calculation involves the circle's radius (the distance from the center to any point on the edge) or its diameter (the distance across the circle through its center, which is twice the radius).
Formula: Circumference = 2 × π × radius
Where π (pi) is a mathematical constant approximately equal to 3.14159.
Example: A circular fountain has a radius of 3 meters. Its circumference is 2 × π × 3 ≈ 18.85 meters.
4. Triangle
A triangle is a polygon with three sides. To find its perimeter, you simply add the lengths of all three sides.
Formula: Perimeter = Side A + Side B + Side C
Example: A triangular plot of land has sides measuring 7 meters, 8 meters, and 10 meters. Its perimeter is 7 + 8 + 10 = 25 meters.
It's important to remember the Triangle Inequality Theorem: the sum of the lengths of any two sides of a triangle must be greater than the length of the third side. Our calculator includes a check for this to ensure valid triangle dimensions.
Using the Perimeter Calculator
Our easy-to-use calculator simplifies the process of finding the perimeter for various shapes:
- Select Your Shape: Choose from Square, Rectangle, Circle, or Triangle using the dropdown menu.
- Enter Dimensions: Input the required measurements (side length, length/width, radius, or three side lengths) into the designated fields.
- Calculate: Click the "Calculate Perimeter" button.
- View Result: The calculated perimeter will be displayed instantly, helping you quickly get the measurements you need for your projects.