How this fence calculator works
The calculator assumes a wood fence with pickets nailed or screwed to horizontal 2×4 rails running between posts. Gates count as their own openings, so the gate width is subtracted from the fenced length and every gate gets a post on each side.
How many fence posts do I need?
Divide the fenced length by the post spacing and round up to get the number of sections, then add one post to close the run, one per gate, and one per corner. For a straight 100 ft fence with 8 ft spacing that's 13 sections and 14 posts.
How deep should fence posts be?
A common rule is to bury at least one third of the post's above-ground height, and never less than 2 ft. A 6 ft fence needs posts about 2 ft deep (8 ft posts), and an 8 ft fence needs about 3 ft (12 ft posts). In cold climates, dig below your local frost line; your building department can tell you how deep that is. For gate posts, frost depth and hole sizes, use the fence post depth calculator.
How much concrete per fence post?
Dig holes about three times the width of the post: roughly 10–11″ across for a 4×4 and 16–17″ for a 6×6. A 2 ft deep hole for a 4×4 takes about 1 cubic foot of concrete, which is just under three 50 lb bags of fast-setting mix or about two 80 lb bags of standard mix. The fence post concrete calculator covers other hole sizes and bag weights.
How many pickets do I need?
Convert the fence length to inches and divide by the picket width plus any gap. A 1×6 picket is actually 5½″ wide, so 100 ft of privacy fence needs about 219 pickets. The calculator adds 5% for split or warped boards. For spaced or board-on-board fences, use the fence picket calculator.
How many rails per section?
Use 2 rails for fences up to 4 ft, 3 rails up to 6 ft, and 4 rails for anything taller. Rails span from post to post, so with 8 ft spacing each rail is one 2×4×8.
What's not included
- Screws or nails (budget about 5% of the material cost)
- Gravel for drainage under each post
- Post caps, stain or sealer
- Labor if you hire a pro