Fence Calculator
Posts, rails, pickets and concrete for a wood picket or privacy fence, with gates subtracted and a cost from your local prices.
Posts
15× 10 ft 4×4
- Rails (3 per section)
- 36 × 8 ft
- Pickets
- 229
- Concrete, 50 lb bags
- 47
- Picket screws/nails
- 1,374
- Sections
- 13
- Material estimate
- $1,655.80
Pickets include 5% extra. For a fence with corners, run it once per straight side and share the corner posts. Gates need hinges, a latch and a diagonal brace.
How the fence math works
- Posts: fenced length (without gates) ÷ post spacing, rounded up, plus one end post, plus one extra per gate.
- Rails: sections × rails per section (2 up to 4 ft, 3 up to 6 ft, 4 for taller).
- Pickets: length in inches ÷ (picket width + gap).
- Concrete: hole volume minus post volume, at 0.375 ft³ per 50 lb bag.
Before digging, call 811 in the US (free utility locating) and check your property line, HOA rules and local height limits; many towns cap backyard fences at 6 ft and front-yard fences at 3–4 ft.
Ask the shop
Stuck on a detail? Ask a question about this job. Your current inputs and results are sent along so the answer fits your numbers. AI answers can be wrong, so double-check anything structural with your building department.
Questions people ask
How many fence posts do I need?
Divide the fence length by the post spacing (usually 8 ft, or 6 ft for tall or windy sites), round up, and add one for the end. Every corner shares a post, and each gate adds one post (a gate needs a post on both sides). A 100 ft run at 8 ft spacing needs 14 posts.
How many pickets do I need for a fence?
Fence length in inches ÷ (picket width + gap). With 5½" pickets and a 1" gap, 100 ft (1,200") needs 185 pickets. For a solid privacy fence with no gap, 1,200 ÷ 5.5 = 219. Subtract gate openings, then add about 5% for splits and bad boards.
How deep should fence posts be?
A common rule is one-third of the post length in the ground, or at least 2 ft, and below the frost line in cold climates. A 6 ft fence typically uses 8 ft posts set 24"–30" deep, with the hole about three times the post width (10"–12" for a 4×4).
How much concrete per fence post?
For a 10" hole 30" deep around a 4×4, you need about 1.2 cubic feet, or two 50 lb bags of fast-setting concrete. An 8" hole 24" deep takes about one bag. The calculator subtracts the post volume.
How many rails does a fence need?
Two rails for fences up to about 4 ft, three rails for 5–6 ft fences (top, middle and bottom), and four for 8 ft privacy fences. Rails span post to post, so buy 8 ft 2×4s for 8 ft post spacing.