Contractor & construction
Siding Calculator
Works siding quantities, where the trim pieces are a large part of the order.
Result
A siding square covers 100 square feet. Openings are not deducted because offcuts around them are usually unusable, on a wall with very large glazing, deduct manually.
Get a Free Business AuditHow the calculation works
Wall area less large openings, divided by the coverage per unit, with a waste allowance, plus starter strip, corner posts, trim and channel around openings. The trim is a substantial share of a siding order and is the part most often underestimated.
What moves the number
- Wall area and the openings deducted.
- Waste allowance, which varies by material and pattern.
- Linear feet of corners, trim and channel.
- Gable ends, which generate heavy cut waste.
Where this one goes wrong
Gables, dormers and anything with angles generate far more waste than a flat wall, because the cuts cannot be used elsewhere, which means a single waste percentage across a whole house underestimates the complex elevations. Measure the trim in linear feet from the elevations, since corner posts, J-channel around every opening and starter strip add up to a quantity nobody estimates accurately by eye.
Before you quote
- Raise the waste allowance for gables, dormers and angled cuts.
- Measure trim and channel in linear feet from the elevations.
- Include starter strip and corner posts in the takeoff.
Questions
About this calculator
How much waste should siding allow?
More on complex elevations than flat walls, because angled cuts at gables and dormers cannot be used elsewhere. A single percentage across a whole house underestimates the complex elevations and oversupplies the simple ones.
What is most often underestimated?
Trim: corner posts, J-channel around every opening, starter strip and finish trim. Measured in linear feet from the elevations it is a substantial share of the order, and nobody estimates it accurately by eye.
Should openings be deducted?
Large ones yes, and the cuts around them generate waste that partly offsets the saving. Small openings are generally better left in the area, since deducting them tends to leave the order short once the cutting is done.
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How to use this calculator
- Total wall length (ft) (ft). Enter your own figure; the page starts at 140 ft.
- Average wall height (ft) (ft). Enter your own figure; the page starts at 10 ft.
- Coverage per square (sq ft) (sq ft). Enter your own figure; the page starts at 100 sq ft.
- Waste allowance (%). Cuts around windows, doors and corners.
- Cost per square ($). Enter your own figure; the page starts at $240.
The result updates as you type, so you can try a figure, see what it does to squares needed, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Total wall length (ft) | 140 ft |
| Average wall height (ft) | 10 ft |
| Coverage per square (sq ft) | 100 sq ft |
| Waste allowance | 12% |
| Cost per square | $240 |
What comes out
| Result | Value |
|---|---|
| Squares needed main result | 16 |
| Area | 1,400.0 |
| Area including waste | 1,568.0 |
| Estimated material cost | $3,840 |
| Approx. trim (linear ft) | 49 |
For 1,400.0 sq ft plus 12% waste you need 16 squares, costing about $3,840.
How sensitive the answer is
Holding everything else steady and changing only cost per square, this is what happens to squares needed. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Cost per square ($) | Squares needed |
|---|---|
| $120 | 16 |
| $180 | 16 |
| $240 example above | 16 |
| $360 | 16 |
| $480 | 16 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Total wall length (ft) (ft)
- Measured in ft, starting at 140 ft.
- Average wall height (ft) (ft)
- Measured in ft, starting at 10 ft.
- Coverage per square (sq ft) (sq ft)
- Measured in sq ft, starting at 100 sq ft.
- Waste allowance (%)
- Cuts around windows, doors and corners.
- Cost per square ($)
- A money amount, starting at $240.
What the results tell you
| Result | What it is |
|---|---|
| Squares needed | The headline result. A number. |
| Area | A decimal figure. |
| Area including waste | A decimal figure. |
| Estimated material cost | A money figure. |
| Approx. trim (linear ft) | A number. |
Overhead is where these go wrong
Pricing and margin figures are only as good as the cost you put in. If your cost covers parts and wages but not the van, the insurance, the phone and the unbilled hours, the markup is paying for those before it becomes profit, and the margin you think you are making is not the one you are making.
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