Quick answer: pickets = fence length ÷ (picket width + gap), rounded up; rails = sections × rails per section; posts = sections + 1 per side, plus a post for each gate.
How to calculate a wood fence
- Measure each straight side and note its gates. Fence length = side − gates × gate width.
- Sections = fence length ÷ post spacing, rounded up, plus one per gate (a gate splits the side).
- Posts = sections + gates + 1 on each side; joined sides share the corner post.
- Rails = sections × 2, 3 or 4. Pickets = fence length (in inches) ÷ (picket width + gap), rounded up.
Example: a 60 ft picket fence with one gate
One 60 ft side, one 4 ft gate, posts every 8 ft, two rails, 3½ in pickets with 2 in gaps:
- Fence length 60 − 4 = 56 ft. Sections ⌈56 ÷ 8⌉ + 1 = 8. Posts 8 + 1 + 1 = 10.
- Rails 8 × 2 = 16, each up to 8 ft.
- Pickets ⌈672 ÷ 5.5⌉ = 123, each 4 ft: 492 ft of pickets.
Counts are whole pieces before spares. No building code, permit or HOA rule is applied; check yours before you build.
Frequently asked questions
How many pickets do I need for a wood fence?
Divide the fence length by the picket width plus the gap and round up. 56 ft of fence with 3½ in pickets and 2 in gaps is 672 in ÷ 5.5 in = 122.2, so 123 pickets.
How many rails does a wood fence need?
Two rails per section is common for fences up to about 4 ft, three for taller fences such as 6 ft privacy fences. The rails span from post to post, so rail length matches the post spacing.
What size lumber is a 1×4 or 1×6 picket?
Nominal sizes are larger than the actual board: a 1×4 is about 3½ in (89 mm) wide and a 1×6 about 5½ in (140 mm). Enter the actual width you measure or the one on the label.
How far apart should wood fence posts be?
Commonly 6 to 8 ft (1.8 to 2.4 m) on centre. 8 ft suits standard 8 ft rails; shorter spacing makes a stiffer fence in windy places.
How much extra should I buy?
The counts are whole pieces with no waste. Add a few spare pickets for splits and bad boards, and check the rails you buy are long enough for your post spacing.
Is this wood fence calculator free to use online?
Yes. The CalcWall Wood 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.