Board And Batten Calculator

Background.

Board and batten is a traditional way to clad barns and houses: wide boards run vertically with a narrow gap between each pair, and a slim strip — the batten — is nailed over every gap to keep rain out of the joint. The gap is deliberate. Wood swells and shrinks across its width as it takes up and loses moisture, and a board fixed tight against its neighbour has nowhere to go. Spaced boards can move under the battens without buckling or splitting.

That spacing is what makes the material count less obvious than it looks. A board does not cover just its own face width; it covers its width plus the gap beside it, and the gap is whatever is left of the batten after it laps onto the boards on both sides. With 250 mm boards, 50 mm battens and 15 mm of overlap on each edge, the gap is 20 mm and the pattern repeats every 270 mm. Divide the wall width by that repeat, round up, and you have the boards. Battens sit only on the joints between boards, so there is always one fewer batten than boards.

Two inputs move the answer more than people expect. Overlap is one: lap the battens a full 25 mm onto each board and the gap closes, the repeat shrinks to the bare board width, and a 9 m wall needs 36 boards instead of 34. The other is lumber sizing. A US "1×10" is about 235 mm across, not 254, and typing the nominal figure undercounts.

The counts assume each board runs the full height of the wall in one piece and that the wall is a plain rectangle. Windows, doors, corner boards and starter trim are left to you, and the waste percentage is applied to the area figure only, never to the board and batten counts.

What is board and batten calculator?

In board-and-batten cladding the repeating unit is one board plus the gap to the next board. Its width, the coverage module, is the board's face width plus the batten's face width, minus the two strips where the batten laps onto the boards on either side. Everything else follows from it: the board count is how many modules it takes to span the wall, rounded up to whole boards, and the batten count is the number of joints between those boards. The area figure is simply the wall face, width times height, with a waste allowance added on top.

How to use this calculator.

1. 01Measure the wall width along its base, corner to corner, and the height from the bottom edge of the cladding to the top, both in metres. Measure the whole face as if it had no openings; the page assumes a plain rectangle.
2. 02Enter the actual face width of your boards and battens, not the nominal size. A US 1×10 measures 9¼ inches (about 0.235 m) and a 1×3 measures 2½ inches (about 0.064 m). If your supplier quotes millimetres, divide by 1,000.
3. 03Set the overlap: how far each batten laps onto each of the two boards beside it. Keep it below half the batten width so a gap remains between the boards, and check the cladding supplier's minimum overlap if they publish one.
4. 04Choose a waste allowance for the area figure. The default is 10%; raise it for a wall with several openings or when the board lengths you can buy will leave long offcuts.
5. 05Read the board and batten counts as full-height pieces. If the wall is taller than the longest boards available, each column will need a joint, and lengths have to be worked out separately.

The formula.

Module = b + w − 2o, where b is the board face width, w the batten face width and o the overlap of a batten onto each board. The term w − 2o is the gap between neighbouring boards, the part of the batten not lying on a board. Boards = ⌈W ÷ module⌉, with W the wall width; the ceiling brackets mean any fraction rounds up to a whole board, so the end boards may need ripping down to fit. Battens = boards − 1, one per joint, with nothing added at the wall ends where corner trim normally finishes the edge. Area = W × H × (1 + waste ÷ 100). The board count is most sensitive to the module: on a 9 m wall, trimming it from 270 mm to 250 mm adds two boards, while wall height and waste do not touch the counts at all. If the overlaps are so large that the module comes out at zero or less, there is no real coverage to count and the page returns an error instead.

A worked example.

Frequently asked questions.

References& sources.

1. [1]U.S. Department of Agriculture Forest Products Laboratory. Wood Handbook 2021. Engineering materials and construction. Retrieved 2026-08-06.
2. [2]National Institute of Standards and Technology. NIST SI Guide, 2008 edition. Appendix B unit relationships. Retrieved 2026-08-06.
3. [3]International Code Council. 2021 International Residential Code. Building construction context. Retrieved 2026-08-06.