Fence Calculator
Calculate how many fence posts, rails, pickets and bags of concrete you need for a wood privacy or picket fence based on its total length and post spacing.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Fence posts
- 14 posts
- 12 sections of 8 ft, plus 1 for gates. Buy 9 ft posts.
- Rails
- 36 rails
- 3 per section, 8 ft long (2x4)
- Pickets
- 210 pickets
- 5.5 in wide with 0 in gap, 6 ft tall
- Concrete
- 28 bags
- 2 x 50 lb (23 kg) bags per post, about 0.39 cu yd
- Screws or nails
- 1,260
- 2 fasteners per picket per rail
Fence formula
Sections = (Fence length - gate widths) / post spacing, rounded up
Posts = Sections + 1 + number of gates
Rails = Sections x rails per section
Pickets = Fence length (in) / (picket width + gap), rounded upWorked example
A 150 ft fence with two 4 ft gates, 8 ft spacing, 3 rails and 5.5 in pickets with no gap: 142 / 8 = 17.75, so 18 sections. Posts = 18 + 1 + 2 = 21. Rails = 18 x 3 = 54. Pickets = 142 x 12 / 5.5 = 310. Concrete at 2 bags per post = 42 bags.
Quick reference
| Fence type | Posts | Rails | Pickets |
|---|---|---|---|
| 4 ft picket, 1 x 4 with 2.5 in gap, 2 rails | 14 | 26 | 200 |
| 6 ft privacy, 1 x 6 no gap, 3 rails | 14 | 39 | 219 |
| 8 ft privacy, 1 x 6 no gap, 4 rails | 14 | 52 | 219 |
How to calculate fence materials
Divide the fence length by the post spacing and round up for the number of sections. Posts are sections plus one, plus an extra post for each gate. A 100 foot fence with 8 foot spacing has 13 sections and 14 posts, or 15 with one gate.
Pickets are the total fence length in inches divided by the width of one picket plus its gap. A 6 foot privacy fence uses about 22 pickets of 5.5 inches per 8 foot section with no gap. Rails are two per section up to 5 feet high and three for 6 feet and taller.
Post depth and concrete
Set posts at least one third of the fence height into the ground, and below the frost line where you have one. A 6 foot fence needs 8 foot posts set 2 feet deep, or 9 to 10 foot posts in cold climates. Each hole takes roughly two 50 lb bags of fast-setting concrete.
Add 10 percent to pickets and rails for splits, warped boards and cuts around gates and corners.
Key facts
- Standard post spacing is 8 ft so rails can be cut from stock 8 ft or 16 ft lumber.
- A 6 ft privacy fence needs 3 rails per section; fences up to 5 ft tall need 2.
- A 6 ft fence uses 8 ft posts set 2 ft deep; set posts below the frost line in cold climates.
- An 8 ft section takes about 18 pickets of 1 x 6 (5.5 in) or 28 pickets of 1 x 4 (3.5 in) with no gap.
Frequently asked questions
How many fence posts do I need for 100 feet?
With 8 foot spacing, 14 posts for a straight run, plus one extra post per gate. With 6 foot spacing, 18 posts.
How many pickets per 8 foot fence section?
About 18 pickets using 5.5 inch (1x6) boards with no gap, or 28 using 3.5 inch (1x4) boards.
How deep should fence posts be?
At least 2 feet for a 6 foot fence, or one third of the post height. Go below the frost line in cold regions to prevent heaving.
How many bags of concrete per fence post?
Two 50 lb bags of fast-setting concrete per post for a 6 foot fence in a 10 inch wide, 2 foot deep hole. Use three bags for larger holes or taller fences.
Sources and references
- QUIKRETE Fast-Setting Concrete Mix product page (50 lb bags for fence posts) (Quikrete)
- Setting Posts project guide: hole diameter and depth (Quikrete)
- Fences for the Farm, Circular 774: post spacing and depth (University of Georgia Extension)
Next steps for this project
The usual order for a framing, decks & fences project. See all framing, decks & fences calculators.
Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.