Shiplap Calculator

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Construction

Calculate the number of shiplap boards needed to cover a wall or ceiling.

Formula

Rows = ⌈wall height / board width⌉; LF = rows × wall width × (1+waste%); Boards = ⌈LF / board length⌉
  • Common shiplap: 1×4 actual 3.5 in wide; 1×6 actual 5.5 in wide; 1×8 actual 7.25 in wide.
  • Overlap (reveal) is usually included in actual face width.
  • Add 10% for simple rooms; 15% for rooms with windows/doors.

12 ft × 9 ft wall, 5.25 in face, 8 ft boards, 10% waste

Inputs
  • Wall Width: 12 ft
  • Wall Height: 9 ft
  • Board Face Width: 5.25 in
  • Board Length: 8 ft
  • Waste %: 10 %

Rows: ⌈9/(5.25/12)⌉ = ⌈9/0.4375⌉ = 21 rows. LF: 21 × 12 × 1.10 = 277 LF. Boards: ⌈277/8⌉ = 35.

Frequently asked questions

What size shiplap should I use?
1×6 (5.5 in face, 5.25 in reveal) is the most popular for modern farmhouse looks. 1×4 gives a busier pattern; 1×8 gives fewer seams.