Shiplap Calculator — Board Count & Material Estimator
Enter your wall dimensions, board length and the exposure width (the visible face after overlap) to calculate exactly how many shiplap boards to buy, including a waste allowance for cuts.
Units
ft
ft
ft
in
%
Total boards including waste allowance — always buy in whole-board quantities
- 1
Wall height in in (same unit as exposure)
8 ft × 12 = 96 inConverting to the same unit as the board exposure width for row counting. - 2
Rows of boards
⌈96 ÷ 5.5⌉ in = 18 - 3
Net linear ft needed
18 rows × 12 ft = 216 ft - 4
Add waste allowance
216 × (1 + 10%) = 237.6 ft - 5
Boards needed
⌈237.6 ÷ 8⌉ = 30
How does this calculator work?
Boards = ⌈Rows × wall width ÷ board length × (1 + waste%)⌉, where Rows = ⌈wall height ÷ board exposure width⌉. Use the exposure (visible face after overlap), not the nominal board width. Allow 10% waste for straight runs, 15–20% for complex layouts.
Formula
How this is calculated
Shiplap is a type of wooden cladding in which each plank has a rabbet (a stepped notch) along its edges, allowing boards to overlap slightly. The key measurement is the exposure width — the visible face after the overlap — rather than the board's full nominal width. For example, a 6-inch nominal board with a ½-inch rabbet on each edge has a 5-inch exposure.
The calculator divides the wall height by the exposure width (rounding up to the nearest whole row) to find how many rows of boards span the wall. Each row needs enough boards to cover the full wall width. The total linear footage is rows × wall width, and the board count is that linear footage divided by the board length, rounded up to whole boards. A waste factor (typically 10% for straight cuts, 15–20% for diagonal or complex layouts) is then applied before the final rounding up — always buy whole boards.
This calculator works for any similar cladding system: tongue-and-groove, board-and-batten (using batten width as the exposure), shiplap siding, or interior feature walls. It does not account for windows, doors or other openings — measure each panel as a separate wall section and sum the board counts.
Frequently asked questions
Shiplap boards are sold by their nominal (full) width, but the visible face is narrower because each edge has a rabbet that overlaps the adjacent board. A 6-inch nominal board typically has a 5–5.5-inch exposure. Always use the exposure width (not nominal) when calculating row count, or you'll underestimate the boards needed.
Allow 10% for simple rectangular walls with horizontal or vertical runs. Increase to 15% if you have many inside corners, complex shapes or diagonal runs (which require angled cuts that waste more material). Add an extra 5% if you are a first-time installer.
Yes — the board-count math is the same. For exterior siding, also account for weather exposure, substrate preparation and any local building-code requirements for underlayment or weather-resistant barriers that are not captured here.
TG we-Calculate Editorial Team. (2026). Shiplap Calculator — Board Count & Material Estimator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/shiplap-calculator
TG we-Calculate Editorial Team. "Shiplap Calculator — Board Count & Material Estimator." TG we-Calculate. 2026. https://we-calculate.com/calculator/shiplap-calculator.
TG we-Calculate Editorial Team, "Shiplap Calculator — Board Count & Material Estimator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/shiplap-calculator
@misc{wecalculate_shiplap_calculator, title = {Shiplap Calculator — Board Count & Material Estimator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/shiplap-calculator}}, year = {2026}, note = {TG we-Calculate} }
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