Quick answer: boards side by side = fence length ÷ board width; board on board = fence length ÷ (board width − overlap), rounded up on each side.
How to calculate a privacy fence
- Enter each side and its gates; the gate openings are taken out of the fence length.
- Sections = fence length ÷ post spacing, rounded up, plus one per gate. Posts = sections + gates + 1 per side, minus shared corners.
- Rails = sections × rails per section (three is common at 6 ft).
- Boards per side = fence length ÷ board width (side by side) or ÷ (width − overlap) (board on board), rounded up.
Example: three sides, one gate
Sides 40, 80 and 40 ft, ends open, a 4 ft gate in the 80 ft side, posts every 8 ft, three rails, 5½ in boards side by side:
- Sections ⌈40 ÷ 8⌉ = 5, ⌈76 ÷ 8⌉ + 1 = 11, 5: 21. Posts 6 + 13 + 6 − 2 shared = 23. Rails 21 × 3 = 63.
- Boards ⌈480 ÷ 5.5⌉ = 88, ⌈912 ÷ 5.5⌉ = 166, 88: 342.
- Board on board with a 1½ in overlap: 120 + 228 + 120 = 468 boards.
Counts are whole pieces before spares. No building code, permit or HOA rule is applied.
Frequently asked questions
How many boards do I need for a privacy fence?
With boards side by side, divide the fence length by the board width and round up: 40 ft of fence with 5½ in boards is 480 ÷ 5.5 = 87.3, so 88 boards. Board on board needs more, because each board overlaps its neighbours.
How do I count boards for a board-on-board fence?
Boards alternate on the front and back of the rails and overlap by the same amount on each side. Each board then adds its width minus the overlap: 5½ in boards with a 1½ in overlap cover 4 in each, so 40 ft needs 480 ÷ 4 = 120 boards.
How tall is a privacy fence?
Privacy fences are often about 6 ft (1.8 m) tall, but the height you may build depends on local rules, which are often lower at the front of a property. Check before you buy.
How many rails does a 6 ft privacy fence need?
Three rails per section is common for a 6 ft fence: top, middle and bottom. Set it to 2 or 4 in the calculator if your design differs.
Should privacy boards have a gap?
Many builders leave boards tight or with a very small gap and let the wood shrink. Enter a gap if you want one; it lowers the board count.
Is this privacy fence calculator free to use online?
Yes. The CalcWall Privacy Fence Calculator is completely free and works online in any browser, on a phone, tablet or computer. There is nothing to download and no account to create, and the math runs right in your browser, so results appear as you type.