How it works
Enter the total run of fence and the post spacing. The calculator divides the run into sections, adds one post to close the last section plus one for each gate, then counts rails and pickets.
Eight feet on center is the standard post spacing for wood fences because rails come in 8 ft lengths. Fences 5 to 6 ft tall usually get three rails to keep pickets from warping. Privacy fences have no gap between pickets; a spaced picket fence typically uses a gap of 1.5 to 3 inches.
Set about one-third of each post's length into the ground, or below the frost line in cold climates. Corners and gate posts take the most load, so many builders use 6 × 6 posts there.
Formula
Sections = length ÷ spacing (rounded up). Posts = sections + 1 + gates. Rails = sections × rails per section. Pickets = length × 12 ÷ (picket width + gap).
Questions people ask
How many posts for a 100 ft fence?
At 8 ft spacing there are 13 sections, which need 14 posts, plus one more for each gate.
How deep should fence posts be set?
A common rule is one-third of the post length in the ground, so a 6 ft fence uses 8 ft posts set about 2 to 3 ft deep. In frost areas go below the frost line, often 36 to 42 inches.
How much concrete per fence post?
A 50 lb bag of fast-setting concrete yields about 0.375 cu ft. A 4 × 4 post in an 8 in hole 2.5 ft deep takes about two bags; a 10 in hole of the same depth takes about three.
How many pickets for an 8 ft section?
With 5.5 in wide pickets and no gap, about 18 pickets cover 8 ft (96 ÷ 5.5 = 17.5).