DIY Home CalcsFence Calculator
Estimate the materials for a wood fence: how many posts, rails and pickets you need for a straight run, including gates. Works for privacy fences (pickets touching) and spaced picket fences.
How the fence calculation works
- Sections = fence length ÷ post spacing, rounded up.
- Posts = sections + 1, plus one extra post for each gate.
- Rails = sections × rails per section.
- Pickets = (fence length − gate widths) × 12 ÷ (picket width + gap), rounded up.
Worked example: a 100 ft privacy fence
- Sections: 100 ÷ 8 = 12.5, so 13 sections.
- Posts: 13 + 1 + 1 gate = 15 posts.
- Rails: 13 × 3 = 39 rails.
- Pickets: (100 − 4) × 12 ÷ 5.5 = 209.5, so 210 pickets.
The gate itself is usually built from the same pickets plus a frame, so buy 8 to 10 extra pickets per gate, along with hinges and a latch.
Lumber sizes
| Part | Typical size | Notes |
|---|---|---|
| Posts | 4 × 4 (3.5 × 3.5 in actual) | Ground-contact rated pressure-treated, or 6 × 6 for gate posts |
| Rails | 2 × 4, 8 ft long | Matches 8 ft post spacing |
| Pickets | 1 × 6 (5.5 in actual) or 1 × 4 (3.5 in actual) | Dog-ear or flat top, 4–6 ft tall |
Before you dig
- Call before you dig. In the US, dial 811 a few days ahead so underground utility lines are marked.
- Check the property line and rules. Local codes and HOAs often limit fence height and how close you can build to the boundary.
- Set posts in concrete or compacted gravel. Use the concrete calculator (round column) for post holes and the gravel calculator for drainage at the bottom of each hole.
Frequently asked questions
How many posts do I need for a 100 ft fence?
With posts every 8 ft, a 100 ft straight run has 13 sections and needs 14 posts. Each gate adds one more post, because a gate needs a post on both sides. Corners and ends of separate runs also add posts.
How far apart should fence posts be?
6 to 8 ft is standard for wood fences, and 8 ft is the usual maximum because rails are commonly sold in 8 ft lengths. Use closer spacing in windy areas or for tall privacy fences.
How many pickets do I need per 8 ft section?
A 1 × 6 board is actually 5.5 in wide. With no gap (privacy fence), an 8 ft section takes 96 ÷ 5.5 ≈ 18 pickets. With a 2.5 in gap (classic picket fence), it takes 96 ÷ 8 = 12.
How many rails per section?
Two rails for fences up to about 4 ft tall and three rails for 5 to 6 ft privacy fences, which keeps pickets from warping.
How much concrete does each fence post need?
A common rule is a hole three times the post width and about one-third of the post's length deep (at least 2 ft, and below the frost line where it freezes). A 10 in hole 3 ft deep is about 1.6 cu ft, or three 80 lb bags; use the concrete calculator's round column option to check your size.