How this calculator works
Worked example: a 125 mm board with a 25 mm overlap covers 100 mm, so a metre of fence takes 10 boards and a 3 m bay takes 30. For 15 m of fence that is 150, and with 5% extra you buy 158. There are 5 bays, so 6 posts, 15 arris rails (3 to a bay) and 5 gravel boards. With 100 mm boards it is 210, with 150 mm boards 126, and a bigger overlap of 50 mm makes it 210. Two rails to a bay need 10, and with no gravel board 0.
Feather edge boards for common lengths of fence (125 mm boards, 25 mm overlap, 5% extra, 3 m bays)
Boards, posts and arris rails.
| Length of fence | Boards | Posts | Arris rails |
|---|---|---|---|
| 3 m | 32 | 2 | 3 |
| 6 m | 63 | 3 | 6 |
| 9 m | 95 | 4 | 9 |
| 12 m | 126 | 5 | 12 |
| 15 m | 158 | 6 | 15 |
| 20 m | 210 | 8 | 21 |
| 30 m | 315 | 11 | 30 |
Tips before you buy
- Set the posts first, and check that they are plumb and in line before you fix the rails.
- Put the first board plumb with a spirit level, and check it every ten boards, because the tapered shape tends to lean.
- Fix each board with two nails through the thick edge, so the thin edge of the next board covers the nails.
- Use a spacer, such as a spare board off-cut, to set the same overlap on each board.
- Finish the fence with a cap and treat the cut ends, to keep the water out of the end grain.
Tools & materials for this project
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Frequently asked questions
How many feather edge boards per metre?
With 125 mm boards and a 25 mm overlap, each board covers 100 mm, so 10 boards for each metre of fence.
How many feather edge boards in a 3 m bay?
30 boards for 125 mm boards and a 25 mm overlap, before the extra for cutting.
How many arris rails do I need?
Three to each bay for a 1.8 m (6 ft) fence: 15 for 5 bays.
Do I need a gravel board?
It is strongly advised: it keeps the bottom of the boards out of the damp ground, and some guarantees need it. It is 150 mm high, so allow for it in the height of the boards.
How do I work out the overlap?
Each board lies over the thin edge of the one before by about 25 mm. A bigger overlap makes a tighter fence but needs more boards.
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Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.