Fiber Cement Calculator

Panel or lap siding quantities from wall area.

Inputs

Gross wall area (sq ft)

Product type (0=lap, 1=panel, 2=shake)

Lap exposure (in)

Plank length (ft)

Window/door openings (sq ft)

Waste allowance (%)

Tab to move between fields

Results

Pieces/panels to order

205

Paint/primer (gal)

Squares (100 sq ft)13

Net siding area (sq ft)1,300

Nail boxes (1 lb)10

Trim (LF)130

Caulk tubes6

How to Use This Calculator

Enter Gross Wall Area in sq ft before openings, then set Product Type (lap, panel, or shake).
For lap siding, set Lap Exposure and Plank Length to match your product; for panels, defaults apply.
Enter Window/Door Openings to subtract, and Waste Allowance (10% typical).
Read Pieces/Panels to Order, Squares Needed, Nail Boxes, Trim (LF), Paint/Primer (gal), and Caulk Tubes.
Use the paint/primer quantity alongside your finish schedule — fiber cement requires field painting at all cut edges.

How the result changes with Gross wall area (sq ft)

Gross wall area (sq ft)	Pieces/panels to order	Paint/primer (gal)
5,001	755	28
17,501	2,720	99
32,500	5,077	185
45,000	7,040	256

What each input means

Gross wall area (sq ft): Total exterior wall area before subtracting openings.
Product type (0=lap, 1=panel, 2=shake): 0 for lap/plank siding, 1 for 4×8 panels, 2 for shingle/shake.
Lap exposure (in): Visible exposure height for lap siding (only used for lap type).
Plank length (ft): Length of each lap siding plank (only used for lap type).
Window/door openings (sq ft): Total area of windows, doors, and other openings.
Waste allowance (%): Extra for cuts, corners, and waste.

What each result means

Pieces/panels to order: Siding pieces, panels, or bundles with waste.
Squares (100 sq ft): Net area in roofing-style squares.
Net siding area (sq ft): Wall area minus openings.
Nail boxes (1 lb): Boxes of 6d stainless nails needed.
Trim (LF): Estimated linear feet of J-channel and corner trim.
Paint/primer (gal): Gallons for 2 coats at 350 sq ft/gal.
Caulk tubes: Tubes of paintable caulk for trim joints.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Gross wall area (sq ft) = 1500, Product type (0=lap, 1=panel, 2=shake) = 0, Lap exposure (in) = 7, Plank length (ft) = 12 = 6 input(s) provided
Calculate Pieces/panels to order
Pieces/panels to order = ceil(pieces * (1 + wastePct / 100))
205 = 205
Calculate Paint/primer
Paint/primer = ceil((netArea * 2) / 350)
8 = 8
Calculate Squares
Squares = netArea / 100
13 = 13
Calculate Net siding area
Net siding area
1300 = 1300

Engine last updated August 5, 2026.

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