Fence Calculator
How many posts and pickets for 100 feet of fence? Enter the run, pick post spacing and fence style, and get the full shopping list — posts, rails, pickets, and concrete bags — to price out a build or sanity-check a contractor's bid.
5.5" = 1×6 picket
Post spacing
Rails per section
Posts
14
14 line
Pickets
230
incl. 5% waste
Rails
26
2 per section
Concrete
28
50-lb bags (2/post)
Sections
13
8-ft on center
Fence run
100
ft of pickets
Counts assume each gate is a 4-ft opening framed by two dedicated gate posts. Set posts one-third of their height deep — 2 ft minimum, below the frost line — and two 50-lb bags of concrete suits a 4×4 post in an 8"-diameter hole about 2 ft deep; 10–12" holes need 3–4 bags per post.
How Fence Math Works
The estimate sets posts on 6- or 8-ft centers and rounds partial sections up: 100 ft at 8-ft spacing is ceil(100 ÷ 8) = 13 sections, which takes one more post than sections — 14 — plus two dedicated posts for every 4-ft gate opening. Rails are sections times rails per section (13 × 2 = 26), and pickets divide the run in inches by picket width plus gap: butted 5.5" privacy pickets give ceil(1,200 ÷ 5.5) = 219, padded 5% for waste and culls to 230. Concrete assumes two 50-lb bags per post — right for a 4×4 in an 8"-diameter hole about 2 ft deep — so 14 posts need 28 bags; widen the hole and you need 3–4 bags per post.
Worked example — 100 ft privacy fence, 8-ft spacing
Sections = ceil(100 ÷ 8) = 13 Posts = 13 + 1 = 14 (+2 per gate) Rails = 13 × 2 = 26 Pickets = ceil(1,200" ÷ 5.5") × 1.05 = 230 Concrete = 14 × 2 bags (50 lb) = 28 Post depth rule: bury 1/3 of post height, minimum 2 ft, and below the frost line.
Frequently Asked Questions
How deep should fence posts be?
Bury one-third of the post's height, with a 2-foot minimum, and always get below the frost line in cold climates so heaving doesn't push the posts up. A 6-ft privacy fence on 8-ft 4×4 posts typically gets holes 2 to 2.5 ft deep, with the hole diameter about three times the post width — roughly 10–12" for a 4×4.
How far apart should fence posts be?
8 ft on center is standard for wood privacy fences because rails and prebuilt panels come in 8-ft lengths; drop to 6 ft for heavier panels, windy sites, or shorter rail stock. At 8-ft spacing, 100 ft of fence is 13 sections and 14 posts; at 6 ft it becomes 17 sections and 18 posts.
How many pickets do I need for 100 feet of fence?
Butted 5.5" pickets (a solid privacy fence): 1,200 inches ÷ 5.5 = 219 pickets, plus 5% waste for splits and culls, about 230. Space the same pickets with a 1.75" gap and the count drops to around 175. Each 4-ft gate opening removes fence run but the gate itself still needs pickets, so keep the spares.
How many bags of concrete do I need per fence post?
Two 50-lb bags per post is the standard estimate — about 0.75 cu ft of mixed concrete, which fills an 8"-diameter hole 2 ft deep around a 4×4 with margin. Widen the hole to 10–12" and you need 3–4 bags per post. For 14 posts at two bags each, that's 28 bags, so pricing the larger 80-lb bags is often worth it.