Trapezoid Square Footage Calculator
For rooms, yards, or roof planes with two parallel sides of different length. Formula: ((a + b) / 2) × h.
Last updated:Tip: If you only have the diameter, divide by 2 to get the radius.
L-shape = two rectangles sharing a corner.
Add one row per rectangle and we'll sum them.
Trapezoid Area Formula
A trapezoid has one pair of parallel sides. The area is the average of the two parallel sides multiplied by the perpendicular distance between them: Area = ((a + b) / 2) × h.
- a = 8 ft, b = 14 ft, h = 6 ft → ((8 + 14) / 2) × 6 = 66 sq ft
- a = 20 ft, b = 30 ft, h = 12 ft → ((20 + 30) / 2) × 12 = 300 sq ft
Common Uses
Trapezoidal shapes are common in real-world settings: side yards of homes, certain roof planes, irregular garden beds, and driveway entries that taper. A tapered driveway (10 ft wide at the street, 16 ft wide at the garage, 30 ft long) has an area of ((10 + 16) / 2) × 30 = 390 sq ft.
Frequently Asked Questions
What is the difference between a trapezoid and a parallelogram?
A trapezoid has exactly one pair of parallel sides; a parallelogram has two. If both pairs of opposite sides are parallel, use the rectangle formula.
How do I measure the height of a trapezoid?
Measure the perpendicular distance between the two parallel sides — not the slanted side.