Shiplap, or wood wall and ceiling paneling, is always in style; rustic meets modern. Whether you’re installing it for looks or structure, you need to calculate how many shiplap boards you’ll need so you can avoid running out of material or wasting excess boards.

What is Shiplap?

Shiplap is the term for wooden boards with edges that overlap, and it can be used for walls, ceilings and exterior siding.

• Dimensions of Wall or Ceiling (L×H)
• Shiplap Ship Size (Width/Length)
• Overlap Amount (Impacts coverage per board)
• Wastage Factor (Typically 10-15% more for cutting mistakes)

Now, how to calculate how many shiplap boards you need?

Formula for Total Wall or Ceiling Area

To start, calculate the total area of the wall or ceiling in square inches or square feet.

$A = W \times H$

Where:

• A = Total Area (square feet or inches)
• W = Wall or Ceiling Width
• H = Wall or Ceiling Height

Formula for Effective Shiplap Board Coverage

Each shiplap board overlaps the next, reducing the actual coverage per board. The effective width of a board is:

$W_{\text{eff}} = W_{\text{board}} - O$

Where:

• $W_{\text{eff}}$ = Effective Board Width (after overlap)
• $W_{\text{board}}$ = Total Width of a Single Board
• O = Overlap Amount

Formula for Total Number of Shiplap Boards

To find the total number of boards needed:

$N = \frac{A}{W_{\text{eff}} \times L_{\text{board}}}$

Where:

• NN = Total Number of Boards Required
• A = Total Area (from earlier calculation)
• $W_{\text{eff}}$ = Effective Board Width
• $L_{\text{board}}$ ​ = Board Length

Formula for Extra Boards (Including Wastage)

To account for cutting waste, add a percentage of extra boards:

$N_{\text{final}} = N \times (1 + W_{\text{percentage}})$

Where:

• $N_{\text{final}}$ = Final Board Count (Including Waste)
• N = Total Boards (without waste)
• $W_{\text{percentage}}$ = Waste Factor (e.g., 10% = 0.10)

Example Calculation

Let’s say you want to cover a wall with:

• Width = 12 feet
• Height = 8 feet
• Shiplap Board Width = 6 inches
• Shiplap Board Length = 8 feet
• Overlap = 0.5 inches
• Wastage Factor = 10% (0.10)

Step 1: Convert Dimensions to Inches

$W = 12 \times 12 = 144 \text{ inches}, \quad H = 8 \times 12 = 96 \text{ inches}$

$A = 144 \times 96 = 13,824 \text{ square inches}$

Step 2: Calculate Effective Board Width

$W_{\text{eff}} = 6 - 0.5 = 5.5 \text{ inches}$

Step 3: Calculate the Total Number of Boards

$N = \frac{13,824}{5.5 \times 96}$

$N = \frac{13,824}{528} = 26.2 \approx 27 \text{ boards}$

Step 4: Include Wastage Factor

$N_{\text{final}} = 27 \times (1 + 0.10)$

$N_{\text{final}} = 27 \times 1.10 = 29.7 \approx 30 \text{ boards}$

Thus, you will need at least 30 shiplap boards for this wall.