How this calculator works
Posts are the number of spacings along the fence plus one. Each section between posts gets the chosen number of rails. Pickets are counted by dividing the fence length by one picket plus its gap. Concrete per hole is the hole cylinder minus the space the post takes up.
Posts = round up( Length ÷ Spacing ) + 1
Rails = (Posts − 1) × Rails per section
Pickets = round up( Length×12 ÷ (Picket width + Gap) )
Concrete = π × (Hole dia ÷ 24)² × Depth − Post area × Depth (cu ft per hole)
Assumptions and tips
- Straight fence with no gates. Add a post for each gate side and corner if they are not already on a spacing mark.
- Post hole depth is often about one third of the post’s above-ground height plus local frost depth — check local rules.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Fence length | 100 ft |
| Post spacing | 8 ft |
| Rails per section | 2 rails |
| Picket width | 5.5 in |
| Gap between pickets | 0 in |
| Post hole diameter | 10 in |
| Post hole depth | 30 in |
| Post size | 4×4 (3.5 in) |
| Concrete bag | 50 lb (0.375 cu ft) |
| Result | Value |
|---|---|
| Posts | 14 posts |
| Pickets | 219 pickets |
| Rails | 26 × 8 ft |
| Concrete bags (all posts) | 43 × 50 lb |
| Concrete per post | 3.07 bags |
| Sections | 13 |
Step by step:
- Posts = 100 ÷ 8 → 13 spacings + 1 = 14
- Pickets = 1,200 in ÷ (5.5 + 0) → 219
- Concrete per hole = hole 1.364 − post 0.213 = 1.151 cu ft
- Bags = 1.151 × 14 ÷ 0.375 → 43
Fence materials by length
8 ft spacing, 2 rails, 5.5 in privacy pickets, 10 × 30 in holes, 50 lb bags.
| Fence length | Posts | Pickets | Concrete bags |
|---|---|---|---|
| 50 ft | 8 posts | 110 pickets | 25 × 50 lb |
| 100 ft | 14 posts | 219 pickets | 43 × 50 lb |
| 150 ft | 20 posts | 328 pickets | 62 × 50 lb |
| 200 ft | 26 posts | 437 pickets | 80 × 50 lb |
Common mistakes to avoid
- Forgetting extra posts at gates and corners.
- Digging before calling 811 to mark utilities.
Frequently asked questions
How many pickets for a 100 ft privacy fence?
With 5.5 in pickets and no gap, about 219 pickets.
How much concrete per fence post?
A 10 in × 30 in hole around a 4×4 post takes about 1.1 cu ft — roughly three 50 lb bags of fast-setting mix.