Shiplap boards overlap with a rabbeted edge, so each covers less height than its nominal width – a 1×6 shiplap board usually shows about 5⅛ in. Always calculate with the exposed (coverage) width. Interior accent walls are often done with ⅛-in nickel gaps between boards.
How to use the Shiplap Calculator
- Wall width
- Wall height
- Doors and windows area
- Board exposure (coverage width)
- Board length
- Waste
- Price per board
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the wall width and height, the area of openings, the board exposure, board length, waste and price per board.
Tips for an accurate estimate
- Take measurements at floor level and at the ceiling – walls and rooms are often slightly out of square.
- Use the manufacturer’s coverage, spacing and installation data when it differs from the typical values here.
- Keep a little extra of every finish material for touch-ups and repairs later.
- Check local building codes and permits before structural, electrical, plumbing or gas work.
Common mistakes to avoid
- Sizing heating or cooling equipment by area alone when insulation, windows and climate make a big difference.
- Buying too little paint, stain or flooring and ending up with mismatched batches.
- Overlooking the extra material for steps, railings, gables and trim.
Inputs explained
| Field | What to enter |
|---|---|
| Wall width | Units: ft, m, in, yd, cm |
| Wall height | Units: ft, m, in, yd, cm |
| Doors and windows area | Units: ft², m², yd², acre |
| Board exposure (coverage width) | Choose one: 1×6 – 5⅛ in, 1×8 – 7 in, 1×10 – 9 in, 1×4 – 3¼ in … |
| Board length | Choose one: 8 ft, 10 ft, 12 ft, 16 ft |
| Waste | In % |
| Price per board | Units: /piece |
What each result means
- Net wall area = max([Wall width]×[Wall height] – [Doors and windows area], 0)
- Rows of boards = ceil([Wall height]÷[Board exposure (coverage width)] – 0.000001)
- Linear length = [Net wall area]÷[Board exposure (coverage width)]
- Boards = ceil([Linear length]÷[Board length]×(1 + [Waste]÷100))
- Cost = [Boards]×[Price per board]
Example values
How the main result changes when Wall width changes and everything else stays at the example values above:
| Wall width (ft) | Boards |
|---|---|
| 7 | 19 |
| 10.5 | 28 |
| 14 | 37 |
| 17.5 | 46 |
| 21 | 55 |
| 28 | 73 |
Formula
Rows = ceil(wall height ÷ exposure)Linear length = net area ÷ exposureBoards = ceil(linear length ÷ board length × (1 + waste))Worked example
Inputs — Wall width: 14 ft; Wall height: 8 ft; Doors and windows area: 0 ft²; Board exposure (coverage width): 1×6 – 5⅛ in; Board length: 8 ft; Waste: 10 %; Price per board: $12 /piece.
Results — Net wall area = 112 ft²; Rows of boards = 19; Linear length = 262 ft; Boards = 37; Cost = $444.00.
Frequently asked questions
How many shiplap boards for an 8 × 12 wall?
96 ft² ÷ 0.427 ft (5⅛ in) = 225 linear ft – about 31 boards of 8 ft with 10% waste.
What is the exposure of shiplap?
About ⅝–¾ in less than the board's actual width because of the overlap.
Should shiplap run horizontally or vertically?
Horizontal makes a room look wider; vertical makes ceilings look taller.
What formula does the Shiplap Calculator use?
Rows = ceil(wall height ÷ exposure).