The four measurements
- Overall length: the longest straight side, end to end.
- Overall width: the other long side, measured at right angles to the first.
- Cut-out length: how far the missing corner runs along the overall length.
- Cut-out width: how far the missing corner runs along the overall width.
Picture the L as a full rectangle with one corner bitten out. Area = overall length × overall width − cut-out length × cut-out width.
Worked example
A patio that is 20 ft by 15 ft overall, with an 8 ft by 6 ft corner missing:
- Full rectangle: 20 × 15 = 300 sq ft.
- Missing corner: 8 × 6 = 48 sq ft.
- Patio area: 300 − 48 = 252 sq ft.
Check it a second way
Split the same L into two rectangles that don’t overlap. The top strip is the full length by the width that remains beside the cut-out: 20 × (15 − 6) = 180 sq ft. The leg below it is the length that remains beside the cut-out by the cut-out width: (20 − 8) × 6 = 72 sq ft. 180 + 72 = 252 sq ft, the same answer. If your two methods disagree, one measurement is wrong.
The two common mistakes
- Counting the overlap twice. Adding 20 × 15 and 12 × 6 counts the leg twice and gives 372 sq ft, about 48% too much.
- Mixing feet and inches. 15 ft 6 in is 15.5 ft, not 15.6 ft. Divide the inches by 12, or enter it as 15 1/2.
Edges, for edge restraint
An L-shape has six edges. In the example they are 20, 9, 8, 6, 12 and 15 ft, which add up to a 70 ft perimeter. Edges that sit against the house or an existing curb usually don’t need edge restraint, so the paver calculator lets you tick only the open ones.
Is the corner square?
Measure 3 ft along one edge from the corner and 4 ft along the other; mark both points. If the corner is square, the straight line between the marks is 5 ft. For bigger layouts use 6, 8 and 10 ft. If the corners aren’t square, the shape isn’t a true L and the formula will be off.