Board and batten is a layout problem first
Everything downstream — the batten count, the linear feet, the paint, the fastener weight — follows from one decision: how many boards it takes to cross the wall. The calculator divides the wall length in inches by the board width you select and rounds up. Battens are then boards + 1, because a batten lands on every joint between two boards and one more at each outer edge of the run.
The inputs that actually move the number
Board width is the lever. The dropdown offers 8, 10, and 12 inches, and each step up drops the board count and the batten count together. Wall height sets how much material each piece consumes: linear feet are board count × wall height × (1 + waste %), and battens are figured the same way. Waste defaults to 10% and is capped at 30%.
Batten width, by contrast, does nothing to the math. It only relabels the breakdown row and the copied summary. Battens are counted per piece and priced per linear foot, so a wider batten costs more without changing the count — raise the batten cost input rather than expecting the width selector to do it. Board and batten cost inputs both default to per-linear-foot rates you can override with your own supplier pricing; the lumber price page is worth a look before you set them.
The two derived lines round on their own terms. Fasteners are (board LF + batten LF) × 0.02 lbs, rounded up to a whole pound at $5/lb. Paint is wall area ÷ 350 sqft per gallon × 2 coats, rounded up to a whole gallon at $45/gal.
Worked example: a 20 ft × 9 ft wall
Running the defaults — 10 in. boards, 3 in. battens, 10% waste, $1.50/LF boards, $0.75/LF battens — the wall needs ceil(240 ÷ 10) = 24 boards and therefore 25 battens. Board linear feet come to 24 × 9 × 1.10 = 237.6, displayed as 238. Batten linear feet are 25 × 9 × 1.10 = 247.5, displayed as 248.
That prices out at 237.6 × $1.50 = $356 for boards and 247.5 × $0.75 = $186 for battens. Fasteners are ceil(485.1 × 0.02) = 10 lbs, or $50. Paint is 180 sqft ÷ 350 × 2 = 1.03 gallons, rounded up to 2 gallons at $90. Total material lands at $682 across 180 sqft, which works out to about $3.79 per square foot of material before any labor. That per-foot figure is the number worth carrying into a bid, and it is the one to compare against a lap or panel alternative in the siding calculator.
Where the count comes up short
The divisor is whatever width you pick, so if your stock is dressed narrower than its nominal name, enter the actual face width or you will be a board or two short on a long wall. The same applies if you are running a deliberate reveal between boards: enter the effective coverage width, not the board width. The tool also assumes each board runs the full wall height in one piece, so if you are splicing courses with flashing between them, calculate by course length instead. Finally, it handles one wall per run — corners, trim, and returns are not counted, and each elevation should be figured separately and totalled. For a more careful coating quantity across multiple surfaces and primer coats, the paint calculator is the better tool.
Limitations
This is a material estimating and planning aid. It produces quantities and a material budget; it says nothing about how the assembly performs. Weather-resistive barrier, flashing at openings and horizontal joints, drainage gaps, back-priming, fastener corrosion resistance, and fastener spacing and penetration are governed by the siding manufacturer’s installation instructions and the building code your jurisdiction has adopted, and warranty coverage usually depends on following them exactly. Confirm the details against the product literature and your local code official before ordering.
Frequently Asked Questions
Why is the batten count always one more than the board count?
Battens cover every joint between two boards plus both outer edges of the run. With 24 boards laid edge to edge there are 23 interior joints and 2 outer edges, which is 25 battens. That is where the boards + 1 rule comes from, and it is how the calculator counts every time.
Does changing the batten width change the cost?
No. Batten width appears only in the labels on the breakdown table and in the copied summary. It never enters the math, because battens are counted by piece and priced by linear foot, and the piece count comes from the board count. If you move from a 2 in. batten to a 4 in. batten, your real cost per linear foot goes up, so raise the batten cost input yourself.
Does the calculator subtract windows and doors?
No. Wall area is length × height with no openings deducted, and the board count comes from the full wall length. That is usually the right call for siding, since you cut around openings and lose most of the offcuts, but it does mean the paint and cost lines carry that area too. On an elevation that is mostly glass, run the calculation on the net wall segments instead.
How is the paint quantity worked out?
Wall area is divided by 350 sqft per gallon, multiplied by 2 for two coats, then rounded up to a whole gallon at $45 per gallon. The rounding matters on small jobs: a 180 sqft accent wall needs 1.03 gallons of coverage and the tool orders 2, leaving most of a gallon on the shelf. Across a full elevation the rounding is negligible.