Accurately calculate the area of any trapezium or trapezoid
Units
Centimeters (cm)
Meters (m)
Feet (ft)
Inches (in)
Calculation Result:
How to Calculate the Area of a Trapezoid
A trapezoid (also known as a trapezium in British English) is a four-sided polygon with at least one pair of parallel sides. The area represents the total space enclosed within those four boundaries. To find the area, you need to know the lengths of the two parallel sides (the bases) and the perpendicular distance between them (the height).
The Trapezoid Area Formula
The mathematical formula used by this calculator is:
A = ((a + b) / 2) × h
A = Area of the trapezoid
a = Length of the first parallel side (Base 1)
b = Length of the second parallel side (Base 2)
h = Perpendicular height
Step-by-Step Calculation Example
Let's say you have a trapezoid with the following dimensions:
Base a = 8 cm
Base b = 12 cm
Height h = 5 cm
Add the bases together: 8 + 12 = 20 cm
Divide the sum by 2: 20 / 2 = 10 cm
Multiply by the height: 10 × 5 = 50 cm²
The total area of the trapezoid is 50 square centimeters.
Frequently Asked Questions
Can a trapezoid have more than one pair of parallel sides?
Yes. In the inclusive definition of geometry, a parallelogram (which has two pairs of parallel sides) is considered a special type of trapezoid.
What units should I use?
You can use any unit of measurement (inches, feet, meters, etc.), as long as you are consistent across all inputs. The resulting area will always be in "square" units.
function calculateTrapArea() {
var b1 = document.getElementById("baseA").value;
var b2 = document.getElementById("baseB").value;
var h = document.getElementById("trapHeight").value;
var unit = document.getElementById("unitType").value;
var resultDiv = document.getElementById("trapResultContainer");
var output = document.getElementById("trapResultOutput");
var formulaStep = document.getElementById("trapFormulaStep");
if (b1 === "" || b2 === "" || h === "" || b1 <= 0 || b2 <= 0 || h <= 0) {
alert("Please enter valid positive numbers for all fields.");
resultDiv.style.display = "none";
return;
}
var baseA = parseFloat(b1);
var baseB = parseFloat(b2);
var height = parseFloat(h);
// Calculation Logic: Area = ((a + b) / 2) * h
var sumBases = baseA + baseB;
var averageBase = sumBases / 2;
var area = averageBase * height;
// Format area to 2 decimal places if necessary
var finalArea = Number.isInteger(area) ? area : area.toFixed(2);
var unitLabel = unit;
if (unit === "units") {
unitLabel = "square units";
} else {
unitLabel = unit + "²";
}
output.innerHTML = "Area = " + finalArea + " " + unitLabel;
formulaStep.innerHTML = "Calculation: ((" + baseA + " + " + baseB + ") / 2) × " + height + " = " + finalArea;
resultDiv.style.display = "block";
// Smooth scroll to result
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}