You’ll need to calculate the area of a triangle to estimate the square footage of siding or sheathing required for a gable end.

The area of a right triangle is equal to ½ the product of the base times the height, or 1/2 (BXH)= Area

The area calculation for the right triangle below would look like:
1/2 (B X H) = AREA
1/2 (14 X 6) = 42 SQUARE FEET

On a calculator you would perform: 14×6/2.

You can use a shortcut method when estimating the area for a gable end for a roof that has the same pitch on both sides. When you put the two triangles together, they actually make a rectangle.

Now you can multiply the length times the width to calculate the total square footage.

6 X 14 = 84 SQUARE FEET

Divide 84 by 100, and you get .84 square of siding for this gable end(sell one square).

For an equilateral triangle the area is equal to .433 times the square of one side. Each side of an equilateral triangle is the same length.

.433 X S²=AREA

For the equilateral triangle below the calculation would be:

.433 X 8² = AREA
.433 x (8 x 8) = AREA
.433 x 64 = 27.71 SQUARE FEET