Fence calculator
Posts, rails, pickets and bags of concrete for a wood fence, with how long the posts should be and how deep to set them.
Your fence takes
16 posts, 4x4 × 10 ft
- Post length
- 9 ft 0 in
- Post boards
- Longer than 20 ft
- Hole depth
- 36 in
- Hole width
- 10 1/2 in
- Concrete
- 42 × 80 lb (2.6 per post)
- Rails
- 36 × 8 ft
- Pickets
- 210 (1x6)
- Sections
- 12 (96 ft of fence)
- Estimated materials
Posts and holes follow the concrete maker's fence-post method: a third of the post in the ground, a hole three times the post's width. Dig below your frost line where the ground freezes, and call 811 before you dig.
How to figure fence materials
Take out the gates, divide the rest of the fence into sections at your post spacing, then count posts, rails and pickets. Posts and holes follow the QUIKRETE Concrete Mix (No. 1101) data sheet, Method for Setting Fence Posts (revised October 2022).
- Sections = (fence length − gates) ÷ post spacing, rounded up
- Posts = sections + 1, + 1 for each gate and each corner
- Rails = sections × rails per section, each a post spacing long
- Pickets = fence length without gates (in) ÷ (picket width + gap), rounded up
- Post length = height × 3 ÷ 2 (a third in the ground); hole depth = post length ÷ 3; hole width = 3 × the post's width
- Concrete = (hole − post) × posts, in bags of your size
Worked example
Your 100 ft fence less 1 gate(s) of 4 ft is 96 ft, or 12 sections at 8 ft. That's 12 + 1 + 1 + 2 = 16 posts, each 9 ft 0 in long for a 6 ft fence, set 36 in deep in a 10 1/2 in hole. Each hole takes 1.55 cu ft of concrete, so the posts need 24.8 cu ft: 42 bags of 80 lb.
Fence post length, hole depth and concrete
For 4x4 posts (3 1/2 in actual), from the QUIKRETE Concrete Mix (No. 1101) data sheet, Method for Setting Fence Posts (revised October 2022). 80 lb bags at 0.60 cu ft each.
| Fence height | Post length | Buy | Hole depth | Concrete per post |
|---|---|---|---|---|
| 3 ft | 4 ft 6 in | 8 ft | 18 in | 1.3 bags |
| 4 ft | 6 ft 0 in | 8 ft | 24 in | 1.7 bags |
| 5 ft | 7 ft 6 in | 8 ft | 30 in | 2.2 bags |
| 6 ft | 9 ft 0 in | 10 ft | 36 in | 2.6 bags |
| 7 ft | 10 ft 6 in | 12 ft | 42 in | 3.0 bags |
| 8 ft | 12 ft 0 in | 12 ft | 48 in | 3.4 bags |
Fence questions
How deep should a fence post be?
A third of the post's length, per the concrete maker's fence-post method, so a 6 ft fence needs posts 9 ft 0 in long set 36 in deep. Where the ground freezes, go below the frost line your building department lists, and follow local code for anything that carries a load.
How many bags of concrete per fence post?
For a 6 ft fence on 4x4 posts, the 10 1/2 in hole takes 1.55 cu ft, about 2.6 bags of 80 lb. A 6x6 post needs a 16 1/2 in hole and about 6.4 bags. The method also puts 6 inches of dry mix in the bottom of the hole before the post goes in.
How far apart should fence posts be?
Posts are commonly set 6 or 8 ft apart so the rails and panels come out of standard board lengths. Closer posts make a stiffer fence and cost more posts and concrete; switch the spacing above to compare.
How many pickets do I need?
Divide the fence length in inches by the picket width plus the gap. A 1x6 picket is 5 1/2 in wide, so a solid 8 ft section takes 18 pickets; add a gap above for a picket fence.
How long should fence posts be?
One and a half times the fence height, since a third goes in the ground. That's 9 ft 0 in for a 6 ft fence, so buy 10 ft posts and cut the tops level after they're set.