CalculatorEnter your measurements below and it works the answer out.
Wall area divided by 100 sq ft per square, plus 10% waste, rounded up. Trim and corner posts are bought in linear feet separately.
The arithmetic. Work out the area, divide by what one square covers, add 10% waste, round up. Nothing more than that — the value of the page is the coverage figures and the waste allowance, both of which are stated here rather than hidden inside the tool.
Why the waste allowance is 10%. A square is 100 square feet — the unit the whole exterior trade quotes in, for siding and roofing alike. Ten per cent covers cuts at corners and openings; a house with a lot of gables and dormers wants fifteen.
How it is sold. Siding is sold by the square, and vinyl usually comes two squares to a box. Trim, corner posts and J-channel are counted in linear feet separately and are not in this figure.
Count the walls, and count the trim separately. Gross wall area is the figure to work from — deduct a garage door, not a window. Corner posts, J-channel, starter strip and soffit are bought in linear feet and are not in the square count at all.
Round up to how it is sold. The result below shows three numbers: the raw quantity, the quantity after the 10% allowance, and the whole squares to buy. You can see exactly where the rounding happened rather than being handed one figure.
Divide your area in square feet by the coverage of one square, then add 10% and round up. At 100 sq ft each, a 200 sq ft job needs 3.
10% is what this calculator adds. A square is 100 square feet — the unit the whole exterior trade quotes in, for siding and roofing alike. Ten per cent covers cuts at corners and openings; a house with a lot of gables and dormers wants fifteen.
100 square feet. It is the unit the exterior trades quote in, so a 1,500 square foot wall area is 15 squares before waste.
Free to use on any site, including commercial ones. Paste this where you want it to appear — it keeps working when we update the figures.