Siding calculator: how much siding do I need?
40 panels
320 square feet of surface · for 40 × 8 ft
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Enter it the way you measured it: 4.5, 4 1/2,
3/8 or 10' 6".
40 panels
320 square feet of surface
A 320 square foot wall takes 40 siding panels of 12 ft by 8 in exposure, because each panel covers 8 square feet. Panels come boxed, so divide by the count on your box.
A worked example
A 23 by 9 ft wall in 12 ft panels of 10 in exposure, with an 8% waste allowance needs 23 panels. 207 square feet at 10 square feet per panel is 20.7, and the 8% allowance takes it to 23.
What else it is called
Exposure is also printed as the profile name: double 4 in means two courses of 4 in, so 8 in of exposure, and double 5 in means 10 in. What this page needs is the inches left showing, whatever the label calls it.
Common sizes
| Area | 12 ft × 8 in exposure | 12 ft × 9 in exposure | 12 ft × 10 in exposure | 12 ft 6 in × 8 in exposure | 12 ft 6 in × 9 in exposure | 12 ft 6 in × 10 in exposure |
|---|---|---|---|---|---|---|
| 8 × 8 ft — 64 sq ft | 8 | 8 | 7 | 8 | 7 | 7 |
| 10 × 10 ft — 100 sq ft | 13 | 12 | 10 | 12 | 11 | 10 |
| 10 × 12 ft — 120 sq ft | 15 | 14 | 12 | 15 | 13 | 12 |
| 12 × 12 ft — 144 sq ft | 18 | 16 | 15 | 18 | 16 | 14 |
| 12 × 16 ft — 192 sq ft | 24 | 22 | 20 | 24 | 21 | 19 |
| 16 × 20 ft — 320 sq ft | 40 | 36 | 32 | 39 | 35 | 31 |
| 20 × 20 ft — 400 sq ft | 50 | 45 | 40 | 48 | 43 | 39 |
Pieces, rounded up, with no waste allowance added.
Where the numbers come from
- A panel covers its length times its EXPOSURE, which is the part left showing once it laps the course below: a 12 ft panel with 8 in of exposure covers 8 square feet. Both figures are the ones you read off the panel, so none of them is ours to source.
- This page counts PANELS, not squares. The trade sells siding by the square, meaning 100 square feet, and by the box; this page does not use that unit because the panels per box vary by maker and we would have to source it. Divide the count by the panels printed on your box.
This counts the flat wall area you type in. It does not subtract windows and doors, it does not add the extra laps a gable or a corner needs, and it counts no trim: starter strip, J-channel and corner posts are sold by the piece and are not on this page.
By Javier Miralles · Last updated . How this site is made.
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