Rectangle Area & Perimeter Calculator
Meters (m)
Feet (ft)
Inches (in)
Centimeters (cm)
Yards (yd)
Calculated Area:
Calculated Perimeter:
Please enter valid positive numbers for both length and width.
function calculateRectangle() {
var length = parseFloat(document.getElementById('rectLength').value);
var width = parseFloat(document.getElementById('rectWidth').value);
var unit = document.getElementById('rectUnit').value;
var areaOutput = document.getElementById('areaOutput');
var perimeterOutput = document.getElementById('perimeterOutput');
var resultsDiv = document.getElementById('rectResults');
var errorDiv = document.getElementById('rectError');
if (isNaN(length) || isNaN(width) || length <= 0 || width <= 0) {
resultsDiv.style.display = 'none';
errorDiv.style.display = 'block';
return;
}
errorDiv.style.display = 'none';
var area = length * width;
var perimeter = 2 * (length + width);
// Unit formatting logic
var areaUnit = unit === 'meters' ? 'sq m' :
unit === 'feet' ? 'sq ft' :
unit === 'inches' ? 'sq in' :
unit === 'centimeters' ? 'sq cm' : 'sq yd';
var linearUnit = unit === 'meters' ? 'm' :
unit === 'feet' ? 'ft' :
unit === 'inches' ? 'in' :
unit === 'centimeters' ? 'cm' : 'yd';
areaOutput.innerText = area.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 4}) + ' ' + areaUnit;
perimeterOutput.innerText = perimeter.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 4}) + ' ' + linearUnit;
resultsDiv.style.display = 'block';
}
How to Calculate the Area of a Rectangle
Understanding the area of a rectangle is a fundamental skill in geometry, architecture, and daily DIY projects. Whether you are measuring a room for new flooring or calculating the size of a garden bed, the math remains the same.
The Area Formula
The area of a rectangle represents the total space contained within its four sides. To find this value, you simply multiply the length by the width. The formula is expressed as:
Area = Length × Width
The Perimeter Formula
While the area tells you the space inside, the perimeter tells you the total distance around the outside. This is useful for fencing or baseboards. The formula is:
Perimeter = 2 × (Length + Width)
Practical Example
Imagine you have a living room that is 15 feet long and 12 feet wide. To find the total square footage and the trim needed:
- Area: 15 × 12 = 180 square feet.
- Perimeter: 2 × (15 + 12) = 2 × 27 = 54 linear feet.
Important Tips for Accuracy
- Consistency: Ensure both measurements (length and width) use the same units (e.g., both in meters or both in inches) before you multiply.
- Squaring Units: Remember that area is always measured in "square" units (sq ft, m², etc.) because you are calculating two dimensions.
- Irregular Shapes: If your space isn't a perfect rectangle, try breaking it down into smaller rectangles, calculate each area separately, and then add them together.