# Shiplap Calculator

URL: https://speedycalculator.com/calculators/construction/shiplap/
Last updated: 2026-10-25

> The shiplap calculator works out how many shiplap boards cover a wall from its size, the board exposure and length, less doors and windows, with waste, linear footage and cost.

## Inputs

- Wall width (ft, m, in, yd, cm)
- Wall height (ft, m, in, yd, cm)
- Doors and windows area (ft², m², yd², acre)
- Board exposure (coverage width)
- Board length
- Waste (%)
- Price per board (/piece)

## Results

- Net wall area
- Rows of boards
- Linear length
- Boards
- Cost

## Formula

```
Rows = ceil(wall height ÷ exposure)
Linear length = net area ÷ exposure
Boards = ceil(linear length ÷ board length × (1 + waste))
```

## Explanation

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

FieldWhat to enterWall widthUnits: ft, m, in, yd, cmWall heightUnits: ft, m, in, yd, cmDoors and windows areaUnits: ft², m², yd², acreBoard exposure (coverage width)Choose one: 1×6 – 5⅛ in, 1×8 – 7 in, 1×10 – 9 in, 1×4 – 3¼ in …Board lengthChoose one: 8 ft, 10 ft, 12 ft, 16 ftWasteIn %Price per boardUnits: /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)Boards71910.528143717.54621552873

## 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.

## FAQ

**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).