Shiplap Calculator

How it works

net area = length × height − openings · linear length = net area ÷ exposed width × (1 + waste) · boards = ⌈linear length ÷ board length⌉ · nails ≈ rows × studs × 2

Shiplap and tongue-and-groove boards overlap, so coverage depends on the exposed face, not the nominal width: a 1×6 shiplap board (5½″ actual) shows about 5⅛″ (13 cm), and a 1×8 about 6⅞″ (17.5 cm). Divide the net wall area by that face to get the running length, add 10% for cuts and defects (15% for diagonal patterns or many openings), then divide by the board length. Boards are face-nailed with two nails into every stud, which sit 40 cm (16″) apart, or blind-nailed through the tongue on tongue-and-groove.

Worked example

A 4 m wall 2.5 m high with 2 m² of openings leaves 8.0 m² to cover. With 1×6 shiplap showing 13 cm, that is 8 ÷ 0.13 = 61.5 m of board, or 67.7 m with 10% waste, so 67.7 ÷ 3.05 = 22.2 → 23 boards of 3.05 m (10 ft), costing $276.00 at $12 each. The wall takes 20 rows of boards and about 440 nails (2 per stud, 11 studs).

Sources: Western Wood Products Association — lumber sizes · USDA Forest Products Laboratory — Wood Handbook

Frequently asked questions