How this calculator works
It splits the fence into sections at your post spacing, counts one post per section plus the end post and one more for each corner, and adds rails: two per section up to 5 ft high, three above that. Pickets are the fence length divided by the picket width plus any gap, with a little waste.
Posts are sized to bury about a third of the fence height, and never less than 2 ft (0.6 m), then rounded up to a stock length. Where the ground freezes, local code may require posts set deeper, below the frost line.
sections = fence length ÷ post spacing, rounded up
posts = sections + 1 + corners
rails = sections × (2, or 3 above 5 ft)
pickets = fence length × 12 ÷ (picket width + gap) × (1 + waste)Worked example
A 100 ft, 6 ft high privacy fence with posts 8 ft apart has 100 ÷ 8 = 12.5, so 13 sections. That takes 13 + 1 + 2 corners = 16 posts of 8 ft and 13 × 3 = 39 rails. With 5½″ pickets and no gap, 1,200 ÷ 5.5 = 218.2 pickets; with 5% waste the list buys 230.
Tips before you buy
- Call your local utility locating service before digging post holes.
- Check property lines, HOA rules and local height limits before you buy anything.
- Each gate needs a strong post on both sides; add a post for each gate opening and buy the gate kit separately.
- Use pressure-treated posts rated for ground contact, and set them in concrete or compacted gravel.
- Pickets are attached with two exterior-rated fasteners per rail; check the box count when you buy screws or nails.
Questions
- How far apart should fence posts be?
- Eight feet (about 2.4 m) is the usual maximum for wood fences, because rails come in 8 ft lengths. Closer spacing, such as 6 ft, makes a stiffer fence and suits tall fences in windy areas.
- How deep should fence posts be set?
- A common rule is to bury about one third of the post’s above-ground height, at least 2 ft. In cold climates set them below the frost line so frost heave does not lift them; your local building department can tell you the depth.
- How many rails does a fence need?
- Fences up to about 5 ft high usually have two rails per section, near the top and bottom. Taller privacy fences add a third rail in the middle to keep the pickets from warping.
- How much concrete do the posts need?
- That depends on the hole diameter and depth. Use the fence post concrete calculator in the Concrete aisle with your post count to get the number of bags.