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Woodshop Math

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Fence Board Calculator

Estimate fence boards or pickets, posts, rails, waste, and optional material cost.

Fence board calculator

After you calculate, print and download options will appear.

Result

Enter fence dimensions, board or picket spacing, posts, rails, and optional prices.

These results are estimates only. Verify measurements, material specifications, structural requirements, safety requirements, and local building rules before buying materials or building.

How this calculator works

This fence board calculator estimates vertical boards or pickets, posts, rails, waste, and optional material cost for a simple straight fence. It supports metric and imperial inputs and preserves the currency symbol you enter without conversion.

Use actual board or picket width, planned gap, post spacing, rail stock length, and the lumber/timber prices that match your supplier. Post spacing depends on fence design, materials, wind exposure, soil, height, gates, and local building rules.

Formula

  • Boards or pickets = ceiling((fence_length + gap) / (board_width + gap)).
  • Posts = ceiling(fence_length / post_spacing) + 1.
  • Total rail length = fence_length x rail_rows.
  • Rail pieces = ceiling(total_rail_length / rail_stock_length).
  • Boards with waste = ceiling(boards x (1 + waste_percent / 100)).
  • Rail pieces with waste = ceiling(rail_pieces x (1 + waste_percent / 100)).
  • Optional total cost = boards_with_waste x price_per_board + posts x price_per_post + rail_pieces_with_waste x price_per_rail_piece.

Worked example

For a 20 m fence with 140 mm boards and 10 mm gaps, the board coverage is 150 mm. Boards = ceiling((20 + 0.01) / 0.15) = 134.

With 2.4 m post spacing, posts = ceiling(20 / 2.4) + 1 = 10. With two rail rows, total rail length is 40 m. If each rail piece is 4.8 m, rail pieces = ceiling(40 / 4.8) = 9 before waste.

Common mistakes

  • Using nominal board width instead of the actual measured board or picket width.
  • Forgetting that gaps change the board or picket count.
  • Treating one straight run as a full fence layout when gates, corners, slopes, steps, and bracing need separate planning.
  • Assuming one post spacing works for every fence design, material, site, and local requirement.

FAQs

How many fence boards do I need?

Enter the fence length, actual board or picket width, and planned gap. The calculator estimates boards with ceiling((fence length + gap) / (board width + gap)).

Does this calculator include gaps between boards?

Yes. The gap is included in the board or picket count. Enter 0 if the boards or pickets are intended to touch.

Does this calculator include fence posts?

Yes. It estimates posts as ceiling(fence length / post spacing) + 1 for a simple straight run.

Does this calculator include rails?

Yes. It multiplies fence length by rail rows, then divides by rail stock length and rounds up to whole rail pieces.

Does this calculator work for metric and imperial?

Yes. Metric inputs use metres and millimetres. Imperial inputs use feet and inches. Lengths are normalized internally before calculating.

Is this a building code or structural calculator?

No. This is for estimating materials only. Verify structural requirements, safety requirements, post spacing, post depth, bracing, gates, wind exposure, soil, and local building rules before building.

Calculator disclaimer

These results are estimates only. Verify measurements, material specifications, structural requirements, safety requirements, and local building rules before buying materials or building.