Siding Calculator
Enter your wall size to get the siding you need in squares and boxes, plus an estimated cost. Waste is included.
Siding needed
Estimated cost
How to calculate siding
Siding is measured in squares, and one square is 100 sq ft. Find the wall area, add waste, divide by 100 for squares, then divide by 2 for boxes, since a box usually covers 2 squares.
Formula: squares = wall area (sq ft) × (1 + waste %) ÷ 100, and boxes = squares ÷ 2, rounded up
Worked example: 40 ft × 10 ft wall
Wall area = 40 × 10 = 400 sq ft. Add 10% waste: 440 sq ft. Squares: 440 ÷ 100 = 4.4 squares. Boxes: 4.4 ÷ 2 = 2.2, rounded up to 3 boxes.
Whole houses
This calculator does one wall at a time. For a whole house, repeat it for each wall and add the boxes. Subtract large openings for an exact count.
Common wall sizes
Cost tips
Prices on this page are editable estimates, not quotes. Get 2 to 3 local quotes before you buy, and ask if delivery is included. Delivery, tax and waste can change the total a lot. Order a little extra for cuts and breakage, and confirm final quantities with your supplier or a qualified professional.
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Frequently asked questions
How much siding do I need for a 40x10 wall?
A 40 ft by 10 ft wall needs 4.4 squares with 10% waste, which is 3 boxes at 2 squares per box.
What is a square of siding?
One square is 100 sq ft. Siding boxes usually cover 2 squares, or 200 sq ft.
How much waste should I add?
Add 10% for plain walls and 15% or more for walls with many windows, doors and corners.
Does this cover a whole house?
No, this is one wall. Repeat it for each wall and add the boxes, or enter the total wall area.
Are the prices accurate?
Prices are editable estimates. The defaults are typical US figures, and your local price can be higher or lower.