Enter the total length of your walls, the wall height and your gable ends, leave out windows and doors, and choose your siding. The calculator gives you squares of siding, the boxes or planks to buy, and the cost if you add prices.
Extra and cost
A square of siding covers 100 square feet. Trim, corners and J-channel are extra; measure them separately.
How to measure for siding
- Wall length: measure all the way around the house and add the walls together.
- Wall height: measure from the bottom of the siding to the eaves.
- Gables: count the triangular gable ends and measure their width. The calculator works out their height from the roof pitch.
- Openings: add up large windows and doors to leave out. Small ones are often left in, because the cut-outs are mostly waste anyway.
Siding formula
- Wall area = total wall length × wall height
- Gable area = ½ × gable width × gable height, for each gable
- Squares = (wall area + gable area − openings) × (1 + extra) ÷ 100
Worked example
A 50 × 30 ft house (160 ft of wall) with 9 ft walls, two 30 ft gables at 6/12, and 180 square feet of windows and doors:
- Walls: 160 × 9 = 1,440 square feet
- Gables: 2 × ½ × 30 × 7.5 = 225 square feet
- To cover: 1,440 + 225 − 180 = 1,485 square feet
- With 10 percent extra: 16.3 squares
- Vinyl: 9 boxes of 2 squares. Fiber cement: 234 planks.
Siding types
| Siding | How it’s sold | Coverage |
|---|---|---|
| Vinyl lap | By the square, in boxes | Boxes often hold 2 squares (200 sq ft) |
| Fiber cement lap, 8¼ in plank | By the plank | 7 in exposure × 12 ft = 7 sq ft per plank |
| Wood lap, shiplap or cedar | By the board or linear foot | Exposure × board length; enter both |
Exposure is the part of each board you can see once it’s installed, not its full width.
Trim and accessories
- Starter strip: runs along the bottom of every wall, so you need about the total wall length.
- Corner posts: one for each outside and inside corner, as tall as the wall.
- J-channel: goes around windows and doors and under the eaves. Measure these separately.
- House wrap: usually goes on before the siding to keep water out.
Siding cost
Siding is usually priced per square for materials and per square for labor. Open “Extra and cost” and enter both to see the total. In the example above, at example prices of $150 per square for materials and $250 for labor, 16.3 squares would cost about $6,534. These prices are only for illustration.
The cost goes up with taller or multi-story walls, lots of windows and corners, removing old siding, and premium materials such as fiber cement or cedar.
Frequently asked questions
How much siding do I need?
Multiply the total wall length by the wall height, add the gables, subtract large openings, add 10 percent and divide by 100 to get squares.
How many square feet are in a box of vinyl siding?
Many boxes hold 2 squares, which is 200 square feet. Check the label, because some brands differ.
How many fiber cement planks do I need?
For 8¼ inch planks with a 7 inch exposure, each 12 ft plank covers 7 square feet. Divide the area by 7 and add extra.
Should I subtract windows and doors?
Subtract large openings like garage doors and big windows. Small ones are often left in to cover cutting waste.
How much does new siding cost?
It depends on the material, the house and your area. Enter local prices per square for materials and labor to see your total.
Results are estimates for planning. Check product coverage and local prices. See How We Calculate for the formulas we use.
Guides for this project
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