A shadow box fence alternates pickets on each side of the rails, so it looks the same from both sides and lets air through.
How the materials are counted
Posts = sections + 1 on each run. Rails = sections × rails per section. Pickets = run length ÷ (picket width + gap), rounded up. Post depth = half the height above ground or the frost depth, whichever is deeper.
Example: a 150 ft, 6 ft tall fence with posts every 8 ft needs 20 posts (10 ft 4×4), 57 rails, 446 pickets and 100 bags of fast-setting concrete.
Materials needed at a glance
Worked out with the same settings as the calculator above, changing only the length.
| Length | Posts | Rails | Pickets | Concrete bags |
|---|---|---|---|---|
| 50 ft | 8 | 21 | 150 | 40 |
| 100 ft | 14 | 39 | 299 | 70 |
| 150 ft | 20 | 57 | 446 | 100 |
| 200 ft | 26 | 75 | 595 | 130 |
| 300 ft | 39 | 114 | 891 | 195 |
Rules of thumb
| Item | Typical |
|---|---|
| Depth in the ground | ⅓ of the post length, or below the frost line |
| Hole width | About 3 × the post width |
| Wood post spacing | 6 to 8 ft |
| Chain link line posts | No more than 10 ft |
| T-posts for barbed wire | 8 to 12 ft |
| Field fence | Wood posts 8–10 ft, T-posts 6–8 ft |
Common questions
How many rails does a fence need?
Two rails for fences up to about 4 ft, three for 5 to 6 ft and four for 8 ft fences.
Should posts be 4×4 or 6×6?
4×4 posts are standard for fences up to 6 ft. Use 6×6 for 8 ft fences, gate posts and windy sites.
How long should fence posts be?
Height above ground plus the depth in the ground. For a 6 ft fence that is usually a 9 ft post, so buy 10 ft stock and cut it, or set 8 ft posts deeper only where frost and soil allow.
Sources
- Quikrete, Concrete Mix data sheet (bag yields): https://www.quikrete.com/PDFs/DATA_SHEET-Concrete%20Mix%201101.pdf
- Quikrete, project calculator (post depth example): https://www.quikrete.com/calculator/