Calculating the area of a surface is a fundamental requirement in construction, interior design, gardening, and various mathematical applications. This tool provides an easy way to determine the square footage or square meters of common geometric shapes instantly.
Common Area Formulas
Shape
Formula
Variables
Rectangle
Length × Width
L, W
Circle
π × r²
r (radius)
Triangle
0.5 × Base × Height
b, h
Trapezoid
0.5 × (a + b) × h
a, b (bases), h
Step-by-Step Calculation Example
If you are trying to calculate the area of a rectangular room to install new flooring:
Measure the Length of the room (e.g., 15 feet).
Measure the Width of the room (e.g., 12 feet).
Select "Rectangle" from the dropdown above.
Input 15 and 12 into the respective fields.
The result will show 180 sq. ft. (15 x 12 = 180).
Why Accuracy Matters
Whether you are buying paint, mulch, or floor tiles, an accurate area calculation prevents waste and saves money. Always round your measurements up slightly to ensure you have enough materials for cuts and overlaps in physical projects.
function updateAreaFields() {
var shape = document.getElementById('shapeSelect').value;
var groups = ['grp-rectangle', 'grp-circle', 'grp-triangle', 'grp-trapezoid', 'grp-ellipse'];
for (var i = 0; i < groups.length; i++) {
document.getElementById(groups[i]).style.display = 'none';
}
document.getElementById('grp-' + shape).style.display = 'block';
document.getElementById('areaResult').style.display = 'none';
}
function runCalculation() {
var shape = document.getElementById('shapeSelect').value;
var unit = document.getElementById('unitSelect').value;
var resultArea = 0;
var formulaText = "";
var isValid = true;
if (shape === 'rectangle') {
var l = parseFloat(document.getElementById('rectLength').value);
var w = parseFloat(document.getElementById('rectWidth').value);
if (!isNaN(l) && !isNaN(w)) {
resultArea = l * w;
formulaText = "Formula: Length (" + l + ") × Width (" + w + ")";
} else { isValid = false; }
} else if (shape === 'circle') {
var r = parseFloat(document.getElementById('circRadius').value);
if (!isNaN(r)) {
resultArea = Math.PI * Math.pow(r, 2);
formulaText = "Formula: π × Radius (" + r + ")²";
} else { isValid = false; }
} else if (shape === 'triangle') {
var b = parseFloat(document.getElementById('triBase').value);
var h = parseFloat(document.getElementById('triHeight').value);
if (!isNaN(b) && !isNaN(h)) {
resultArea = 0.5 * b * h;
formulaText = "Formula: 0.5 × Base (" + b + ") × Height (" + h + ")";
} else { isValid = false; }
} else if (shape === 'trapezoid') {
var a = parseFloat(document.getElementById('trapBaseA').value);
var b2 = parseFloat(document.getElementById('trapBaseB').value);
var ht = parseFloat(document.getElementById('trapHeight').value);
if (!isNaN(a) && !isNaN(b2) && !isNaN(ht)) {
resultArea = 0.5 * (a + b2) * ht;
formulaText = "Formula: 0.5 × (Base A + Base B) × Height";
} else { isValid = false; }
} else if (shape === 'ellipse') {
var aVal = parseFloat(document.getElementById('ellA').value);
var bVal = parseFloat(document.getElementById('ellB').value);
if (!isNaN(aVal) && !isNaN(bVal)) {
resultArea = Math.PI * aVal * bVal;
formulaText = "Formula: π × a (" + aVal + ") × b (" + bVal + ")";
} else { isValid = false; }
}
if (isValid) {
document.getElementById('areaResult').style.display = 'block';
document.getElementById('resultDisplay').innerHTML = resultArea.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + " sq. " + unit;
document.getElementById('formulaDisplay').innerHTML = formulaText;
} else {
alert("Please enter valid numeric values for all fields.");
}
}