Fencing · Project planning

Board-on-Board Fence Calculator

Compare continuous lap coverage with a backer-and-cover arrangement. The first lapped board covers its full face width; subsequent boards advance by width minus overlap.

By Alish Gautam, Software Developer · Updated 4 October 2026 · Calculation methodology

Start with the editable example below. Dimensions retain their physical size when units change. Region sets currency labels without converting currencies; confirm entered quotes after changing region.

Fence layout

Run length includes gate openings. Gate offset is measured from the run start. Corner and straight connections share the preceding end post.

Run 1

Run label

Measured run length (ft)

Basic settings

Maximum post spacing (ft)Editable wood-fence planning example. Use project or manufacturer limits.

Calculation modeChoose the estimating method.

Product settings

Product and system dimensions

Actual board face width (in)Editable arithmetic example. Replace with your project or product specification.

Rails per bayEditable arithmetic example. Replace with your project or product specification.

Fasteners per board per railEditable arithmetic example. Replace with your project or product specification.

Lap overlap (in)Editable arithmetic example. Replace with your project or product specification.

Product / specification referenceOptional supplier product name, chart revision or quote reference, saved in shared project state.

Advanced settings

Advanced planning settings

Close perimeterConnect the last run back to the first. All runs must form one connected perimeter.

Board-field reduction from post centres (in)Enter the combined post-face / bracket reduction per bay. Zero treats the equal bay spacing as the clear board field.

Purchase allowance (%)Planning allowance, not a code or industry requirement. Set zero to order the exact rounded takeoff.

Cost settings · USD

Optional quote prices

Price per purchased pack / unitOptional supplier quote in the selected currency. Blank omits cost.

Project takeoff

Whole packages round up. Allowance is separate from purchased surplus. Prices omit labor, delivery, tax and other items unless explicitly entered.

Total measured fence run: 100 ft
Gate openings: 0 ft
Net infill length: 100 ft
Maximum bay spacing: 8 ft
Infill bays: 13
Physical posts: 14
Net requirement: 273 pieces
Allowance: 27.3 pieces
Planned requirement: 300.3 pieces
Unrounded package requirement: 300.3
Boards / pickets to buy: 301
Purchased coverage: 301 pieces
Surplus beyond planned requirement: 0.7 pieces

Supplier-ready material list

line posts: 12
end posts: 2
corner posts: 0
gate posts: 0
Boards / pickets to buy: 301
Rails to buy: 43
Rail installed linear length: 300 ft
Fasteners before reserve: 1,638

Geometry / layout breakdown

Dimensions use the selected measurement system.
Run	Infill (ft)	Bays	Equal spacing (ft)
Run 1	100	13	7.692

Infill span sketch. Shared supports appear in both spans; the physical post total above counts each once. Gate openings are omitted from infill.

The cover must be wider than the selected backer gap. Edge treatment, shrinkage and fastener schedules remain product and project choices.

How it works

Lapped N = 1 + ceil(max(0, field − width) / (width − overlap)). Backer/cover mode counts the back row and a cover board for each internal gap.

Assumptions and limitations

The cover must be wider than the selected backer gap. Edge treatment, shrinkage and fastener schedules remain product and project choices.

Whole packages round upward after the chosen allowance. Physical geometry and purchase reserve are separate. Manufacturer and project specifications override editable examples; the selected region does not establish a local code requirement.

Sources and boundaries

This method uses geometric arithmetic and user-entered dimensions. No installation requirement or material property is inferred from a standard.