# How much board and batten?

A board and batten calculator for a wall: how many vertical battens fit with even gaps no wider than you choose, the exact gap, horizontal rails, the total length and the boards to buy.

- Page: https://www.acalculator.org/construction/board-and-batten-calculator
- JSON spec: https://www.acalculator.org/construction/board-and-batten-calculator.json
- Version: f9aadd808d2c

## Default answer

Example with the default inputs (Wall width 12 ft, Wall height 8 ft, Batten width 2.5 in, Gap between battens, at most 16 in, Horizontal rows 1, Board length 8 ft, Extra for waste 10%): A 12 ft wall takes 9 vertical battens with 15.188 in gaps, 12 boards in all.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| w | Wall width | The width of the wall, edge to edge. |
| h | Wall height | The height to cover, for example from the baseboard up. |
| b | Batten width | The face width of one batten: 2.5 in for a 1×3, 3.5 in for a 1×4. |
| g | Gap between battens, at most | The widest space you want between two battens. |
| rows | Horizontal rows | Battens running across the wall, such as a top rail (1) or a top and middle rail (2). |
| board | Board length | The length of the boards the battens are cut from. |
| waste | Extra for waste | Length to add, in percent, for cut-offs and bad boards. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| battens | Vertical battens | The fewest battens, one at each edge, whose equal gaps are no wider than the gap you chose. |
| gapOut | Gap between battens | The equal space between two battens: (wall width − battens × batten width) ÷ (battens − 1). |
| centers | Center to center | The distance from the center of one batten to the next: gap + batten width. |
| vertical | Length of each vertical batten | The wall height less the horizontal rows. |
| total | Total batten length | Vertical battens × their length + horizontal rows × the wall width. |
| boards | Boards to buy | The total length with the extra for waste ÷ the board length, rounded up. |

## Method

Battens n = ⌈(W − b) ÷ (g + b)⌉ + 1 (at least 2); gap = (W − n × b) ÷ (n − 1); vertical length = H − rows × b; total = n × vertical + rows × W; boards = ⌈total × (1 + waste ÷ 100) ÷ board length⌉.

## Assumptions

- Battens run from edge to edge: one at each end of the wall, with equal gaps between.
- Horizontal rows run the full wall width, and the vertical battens fit between them.
- Boards are counted by total length; the count does not plan each cut. Waste is 10% by default.

## Worked examples

1. w = 3.6576, h = 2.4384, b = 0.0635, g = 0.4064, rows = 1, board = 8, waste = 10% gives battens = 9, gapOut = 0.385763, total = 25.0317, boards = 12. Source: OpenStax Prealgebra 2e, section 9.4 (length and area of rectangles, https://openstax.org/books/prealgebra-2e/pages/9-4-use-properties-of-rectangles-triangles-and-trapezoids); NIST Handbook 44 (1 in = 2.54 cm).
2. w = 3.048, h = 1.524, b = 0.0889, g = 0.3048, rows = 2, board = 8, waste = 0% gives battens = 9, gapOut = 0.280988, total = 18.2118, boards = 8. Source: NIST Handbook 44 (1 in = 2.54 cm).

## FAQ

### How do I space board and batten evenly?

Put a batten at each edge of the wall and space the rest equally. With n battens of width b on a wall W wide, each gap is (W − n × b) ÷ (n − 1). The calculator picks the fewest battens that keep the gap no wider than you ask.

### How many battens do I need for a 12 ft wall?

With 1×3 battens (2.5 in face) and gaps of at most 16 in: (144 − 2.5) ÷ (16 + 2.5) = 7.65, round up to 8, add 1: 9 battens, each gap exactly 15.1875 in (15 3/16 in).

### What is a good batten spacing?

It is a matter of taste and of the wall. Accent walls often use gaps of 12 to 24 in; narrower gaps look busier, wider ones more open. Try a few values and pick the gap you like.

### What size boards are battens?

Common choices are 1×2 (1.5 in face), 1×3 (2.5 in) and 1×4 (3.5 in) boards, or strips of MDF or plywood. Use the actual face width, not the nominal size.

### Does it count a top rail?

Yes: set Horizontal rows to 1 for a top rail, 2 for a top and middle rail, or 0 for vertical battens only. Each row runs the full wall width, and the vertical battens are shortened to fit between the rows.

### How many boards should I buy?

The calculator adds up the length of every batten, adds 10% for waste by default, and divides by the board length. Short pieces can often come from the same board, but buy a spare or two for knots and mistakes.

## Sources

- OpenStax, Prealgebra 2e, section 9.4, Use Properties of Rectangles, Triangles, and Trapezoids (lengths and perimeters of rectangles), CC BY 4.0, retrieved 2026-10-01. https://openstax.org/books/prealgebra-2e/pages/9-4-use-properties-of-rectangles-triangles-and-trapezoids
- NIST Handbook 44 (2024), Appendix C, General Tables of Units of Measurement: 1 in = 2.54 cm, 1 ft = 12 in = 0.3048 m. https://www.nist.gov/pml/owm/nist-handbook-44-current-edition