Board and Batten Calculator
Calculate boards, battens, on-centre spacing and material cost for a board-and-batten wall or siding run, from wall dimensions, board width and batten spacing — including the even spacing you actually mark out.
About this calculator
Board-and-batten almost never divides evenly across a real wall, which is why this calculator's real output is the exact spacing to mark out rather than just a board count. The repeating unit is one board plus one expansion gap, and dividing the wall width by that repeat gives a raw board count that's rounded up to a whole number, since a fractional board isn't buildable. Once that whole-number count is fixed, the calculator works backward to find the actual on-centre spacing across the full wall width — this figure comes out slightly tighter than the nominal board-plus-gap repeat, because rounding the board count up always leaves a little less than one full repeat's worth of extra width to spread across the now-larger number of boards.
A batten covers every seam between boards plus both outer ends, which is why the batten count always comes out to exactly one more than the board count. Vertical runs are calculated separately from horizontal spacing: Pieces per Run accounts for stock boards shorter than the wall height needing to be stacked, and that piece count multiplies through to the linear footage of both boards and battens before a waste percentage is added and the whole thing is priced out.
Inputs
Results
Boards across
17
How to Use This Calculator
- Enter the wall width and height.
- Set the actual face width of your boards and battens — nominal 1×12 and 1×3 stock measure 11.25 in and 2.5 in.
- Choose the gap the battens will cover; solid wood siding needs one for expansion.
- Read the actual on-centre spacing and mark that out rather than the nominal board width.
How the result changes with Board width (in)
| Board width (in) | Boards across |
|---|---|
| 5.63 | 32 |
| 8.44 | 22 |
| 17 | 11 |
| 24 | 8 |
What each input means
- Wall width (ft)
- Width of the wall or elevation to cover.
- Wall height (ft)
- Floor-to-ceiling or sill-to-eave height.
- Board width (in)
- Actual face width of the wide boards (a 1×12 measures 11.25 in).
- Batten width (in)
- Actual face width of the narrow battens (a 1×3 measures 2.5 in).
- Gap between boards (in)
- Expansion gap the batten covers. Leave some for solid wood siding.
- Stock length (ft)
- Length of the boards you are buying.
- Openings to deduct (sq ft)
- Total window and door area.
- Waste factor (%)
- Extra material for cuts and defects.
- Board cost per linear ft ($)
- Price per linear foot of the wide board.
- Batten cost per linear ft ($)
- Price per linear foot of the batten stock.
What each result means
- Boards across
- Number of wide boards across the wall.
- Battens
- One per seam plus one at each end.
- Actual spacing on centre
- Even spacing to mark out — tighter than the nominal repeat once the count is rounded up.
- Batten lap per side
- How far the batten covers each board. Negative means it is too narrow to cover the gap.
- Board to buy
- Linear feet of wide board including waste.
- Batten to buy
- Linear feet of batten including waste.
- Material cost
- Boards plus battens.
- Net wall area
- Wall area less openings.
- Pieces per vertical run
- How many lengths stack to reach the wall height.
How this is calculated
Formula
boards = ⌈wall width ÷ (board width + gap)⌉; spacing = wall width ÷ boards; battens = boards + 1Worked example, using the default values
- Find the repeating unitrepeat = board width + gap11.25 in + 0.5 in = 11.75 in per board
- Divide the wall width by the repeatboards = ⌈wall width ÷ repeat⌉⌈192 in ÷ 11.75 in⌉ = 17 boards
- Re-space evenly across the wallactual spacing = wall width ÷ boards192 in ÷ 17 = 11.29 in on centre
- Add a batten to every seam and both endsbattens = boards + 117 + 1 = 18 battens
- Check the batten covers the gaplap per side = (batten width − gap) ÷ 2(2.5 in − 0.5 in) ÷ 2 = 1 in onto each board
- Convert to linear feet and add wastelinear ft = count × pieces per run × stock length × (1 + waste)boards: 17 × 1 × 10 ft × 1.1 = 188 lin ft board, 199 lin ft batten
Engine last updated . Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why is the actual on-centre spacing always tighter than my nominal board width plus gap?
The raw board count is rounded up to the nearest whole board, since a fractional board can't be installed, which typically leaves a bit less width per board-and-gap unit than the nominal repeat once that whole number of boards is spread evenly across the actual wall width. This tighter, re-spaced figure is what should actually be marked out on the wall — using the nominal repeat instead would leave the last board overhanging past the wall's edge.
Why are there always one more batten than boards?
A batten needs to cover every seam between adjacent boards, and with a given number of boards there are one fewer seams between them than the board count — plus two more battens needed to finish both outer edges of the run. Working through that count, the total always lands at exactly one more batten than the number of boards.
What does a negative Batten Lap per Side actually mean?
It means the batten you've specified is narrower than the gap it's meant to cover, so it physically cannot bridge the seam between boards on either side — the joint will be left open rather than covered. Widening the batten, narrowing the gap, or both is necessary before that combination will actually work as a finished wall.
Why does the calculator round board count and pieces per run up separately instead of combining them?
Board count and vertical pieces per run solve two independent problems — how many boards fit across the width, and how many stock lengths stack to reach the height — so each needs its own rounding to a whole, buildable unit before they're multiplied together for total linear footage. Combining them before rounding would understate how much material is actually needed to cover the full wall.
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