How to calculate fence materials
- Posts: divide the fence length by the post spacing and round up to get sections. You need one more post than sections, plus a post for each corner and each gate.
- Rails: sections × rails per section. Fences up to about 4 ft use two rails; 5–6 ft fences use three.
- Pickets: fence length ÷ (picket width + gap), rounded up. A “6-inch” picket is usually 5.5 in wide.
Worked example: 100 ft of 6 ft privacy fence with 2 corners and a gate
100 ÷ 8 = 12.5, so 13 sections. Posts: 13 + 1 + 2 corners + 1 gate = 17. Rails: 13 × 3 = 39. Pickets: 1,200 in ÷ 5.5 in = 218.2, so 219. Setting 17 posts in 10 in holes, 2 ft deep, takes about 42 bags of 50 lb fast-setting concrete.
How many pickets per 8 ft section?
With 5.5 in pickets butted together, an 8 ft (96 in) section takes about 17.5, so 18 pickets. With a 2.5 in gap it takes 12. Add a few spares for knots and splits.
Post holes
| Post | Typical hole |
|---|---|
| 4 × 4 (3.5 in) | 10–12 in wide |
| 6 × 6 (5.5 in) | 14–18 in wide |
A common rule is to set posts about one-third of the fence height deep, and always below the frost line in cold climates. Gate posts take the most force, so many builders set them deeper. For the exact concrete per hole, the concrete calculator handles round holes too. A few inches of gravel at the bottom of each hole helps drainage.
Before you dig
Call your local utility locate service, confirm the property line, and check height limits and permits with your town or homeowners’ association.