How do I calculate siding?

Total the wall area elevation by elevation (width × height for each wall), subtract the area of large openings like garage doors, entry doors, and big windows, then add about 10% for waste. Divide that by 100 to get the number of squares — the unit siding is estimated and often sold in. This calculator does all of that the moment you enter your wall area.

What is a square of siding?

A square is 100 square feet of coverage — the standard unit for estimating and buying siding. If your walls (after openings and waste) come to 1,500 sq ft, that is 15 squares. Vinyl is commonly sold by the square; converting to squares up front makes ordering and quoting far easier.

How much waste should I add for siding?

About 10% is typical for a straightforward wall. Add more — 15% or higher — for houses with lots of corners, gables, or dormers, or where diagonal and angled cuts create off-cuts you cannot reuse. The calculator lets you set the waste percentage so the estimate matches the complexity of the job.

Does this include trim and soffit?

No — the estimate covers field siding only. Trim, starter strip, J-channel, corner posts, soffit, and fascia are ordered separately by linear foot or piece. Always add those to your material list on top of the squares this calculator returns.

Is the calculator free?

Yes — the live estimate is free with no email required. Enter your email only if you want the free Job Pricing Kit (pricing worksheet, markup cheat-sheet, and invoice + quote templates) sent to your inbox.

Free tool

Siding Calculator

Enter your total wall area and the openings to subtract — get the net area, area with waste, squares needed, and boxes. Free, no signup for the estimate.

Siding estimate

0.0 squares

Net wall area0 sq ft
With waste0 sq ft
Boxes needed—
Squares0.0
Estimated cost—

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How to calculate siding

Siding comes down to one number — how much wall you actually have to cover — and then adding a little for the cuts you will throw away. Total your walls, take out the big openings, add waste, and convert to squares. Get that right on paper and you order the right amount instead of running short or eating the overage.

1. Total the wall area by elevations

Measure each wall — front, back, and both sides — as width × height, and add them together. Include gable triangles (½ × base × height) where the siding runs up into a peak. That combined figure is the gross wall area everything else works from.

2. Subtract the large openings

Take out the area of garage doors, entry doors, and big windows — anything large enough to skip. Small windows are often left in as built-in waste, but pulling the big openings out keeps the estimate honest on a wall that is mostly glass or door.

3. Add about 10% waste

Ten percent is typical for a plain wall. Bump it up for houses with lots of corners, gables, or dormers, or where diagonal and angled cuts leave off-cuts you cannot reuse. The calculator lets you set the waste percentage to match the job.

4. Convert to squares or boxes

Divide the area with waste by 100 to get squares — the standard estimating unit, where one square equals 100 sq ft. If your product lists a coverage per box, the calculator also returns the number of boxes to order so you can buy in the units on the shelf.

One note on how siding is sold: vinyl is usually priced and bought by the square, while fiber-cement and lap siding are sold by the piece or the box. Either way you still order trim, starter strip, J-channel, and corners separately — those are not counted in the field-siding squares here.

Measuring the job is step one. Turning it into a priced, professional quote is faster inside CrewRivet. See the paint calculator, the insulation calculator, or the job pricing calculator.

Siding calculator FAQ

How do I calculate siding?: Total the wall area elevation by elevation (width × height for each wall), subtract the area of large openings like garage doors, entry doors, and big windows, then add about 10% for waste. Divide that by 100 to get the number of squares — the unit siding is estimated and often sold in. This calculator does all of that the moment you enter your wall area.
What is a square of siding?: A square is 100 square feet of coverage — the standard unit for estimating and buying siding. If your walls (after openings and waste) come to 1,500 sq ft, that is 15 squares. Vinyl is commonly sold by the square; converting to squares up front makes ordering and quoting far easier.
How much waste should I add for siding?: About 10% is typical for a straightforward wall. Add more — 15% or higher — for houses with lots of corners, gables, or dormers, or where diagonal and angled cuts create off-cuts you cannot reuse. The calculator lets you set the waste percentage so the estimate matches the complexity of the job.
Does this include trim and soffit?: No — the estimate covers field siding only. Trim, starter strip, J-channel, corner posts, soffit, and fascia are ordered separately by linear foot or piece. Always add those to your material list on top of the squares this calculator returns.
Is the calculator free?: Yes — the live estimate is free with no email required. Enter your email only if you want the free Job Pricing Kit (pricing worksheet, markup cheat-sheet, and invoice + quote templates) sent to your inbox.