Fence Calculator (Posts, Rails, Pickets and Concrete)

Q: How many bags of concrete per fence post?

Two 80 lb bags for a 10 in × 30 in hole around a 4x4; three or four for 6x6 gate posts in deeper holes. The post hole calculator gives the exact figure.

Enter the run of fence, the post spacing, height, rails per section and picket size, and this calculator lists every post, rail and picket with the concrete for the post holes and the fasteners. Gates get their own pair of posts. It covers the common 6 ft privacy fence and 4 ft picket fence and anything in between.

Fence materials calculator

How it works

Sections = (fence length − gate widths) ÷ post spacing, rounded up
Posts = sections + 1, plus 2 per gate
Rails = sections × rails per section
Pickets = fence run × 12 ÷ (picket width + gap), rounded up
Post length = height + about a third for burial + trim, rounded to 8, 10 or 12 ft stock
Concrete = posts × bags per post

Worked example

A 100 ft privacy fence, 6 ft high, posts every 8 ft, three rails, 5-1/2 in pickets butted tight, with one 4 ft gate:

Total fence length: 100 ft
Post spacing: 8 ft
Fence height: 6 ft
Rails per section: 3
Picket width: 5.5 in
Gap between pickets: 0 in
Gates: 1
Gate width: 4 ft
Bags of concrete per post: 2

The calculator gives:

Posts: 14 (12 sections + 1 gate × 2 posts) at 10 ft long
Rails: 36 × 8 ft (288 linear ft; 18 × 16 ft pieces)
Pickets: 210 × 72 in (5.5 in wide, 0 in gap)
Concrete: 28 bags (2 per post)
Picket nails or screws: 1,260 (2 per picket per rail)
Fence run: 96 ft of panels + 4 ft of gates

Twelve sections and 14 posts (10 ft long, to bury 2-1/2 ft), 36 rails of 8 ft, 210 pickets and 28 bags of concrete. Each picket takes six screws over three rails, 1,260 in all. Shadowbox styles that alternate pickets on both sides of the rails need roughly double the pickets.

Notes and limits

Set posts below the frost line where the ground freezes, and never less than a third of the fence height. The post-hole concrete calculator sizes the hole.
Gate posts carry a swinging load: use 6×6 posts and deeper holes for wide gates.
Sloped ground: step or rack the sections; racking needs longer rails or closer posts.
Fence height limits, setbacks and good-neighbour rules are local ordinances; check before buying materials and call 811 before digging.
Pickets are sold by the piece; rails often as 16 ft 2×4 cut in half for 8 ft bays.

Frequently asked questions

How many fence posts for 100 feet?

With 8 ft spacing, 14 posts (13 bays of 8 ft or less). A 4 ft gate takes part of the run but adds a second gate post, so it is still 14. 6 ft spacing needs 18.

How many pickets in a 100 foot fence?

219 pickets of 5-1/2 in width butted tight (210 if a 4 ft gate takes part of the run). With a 2-1/2 in gap and 3-1/2 in pickets, 200.

How far apart should fence posts be?

6 to 8 ft for a wood fence. 8 ft suits standard 16 ft rails cut in half; 6 ft is stiffer and is the usual maximum for 6 ft privacy fences in windy areas.

How many bags of concrete per fence post?

Two 80 lb bags for a 10 in × 30 in hole around a 4×4; three or four for 6×6 gate posts in deeper holes. The post hole calculator gives the exact figure.

How deep should a 6 foot fence post be?

At least 2 ft, and below the frost line. A 10 ft post gives 6 ft of fence, 2-1/2 ft in the ground and some to trim.

Sources

American Wood Council, DCA 6: Prescriptive Residential Wood Deck Construction Guide (Appendix B tributary areas, Table B3 footing sizes; stair stringer rules)

Last reviewed: 26 September 2026. The calculation is covered by automated tests with known answers taken from the sources above. Found an error? Please let us know.