Work out how many posts, rails, pickets and bags of concrete a fence run needs, including the gate openings, using the standard 8-foot post spacing and the actual face width of the boards.
Enter the true perimeter including where the gates go. Picket counts use the actual face width of the board, a 1×6 picket is 5.5 inches wide, not 6.
A fence is a row of bays. You set the posts, then fill the space between them. That is why the post count governs everything else: posts are spaced 8 feet on centre in the most common residential layout, and the run is divided by that spacing to give the number of bays.
Two details trip people up. First, you need one more post than bays, because both ends of the run need a post. Second, every gate adds two posts, one on each side of the opening, and the gate opening itself gets no pickets.
| Component | Typical size | Notes |
|---|---|---|
| Posts | 4×4 for a 6 ft fence, 6×6 for 8 ft | Set 2–3 ft in the ground, below the frost line in cold climates |
| Post spacing | 8 ft on centre | 6 ft adds strength and cost; 10 ft is used for chain link |
| Post depth | Below frost line in cold climates (36–48"). Minimum 1/3 of total post length in ground. | For 6-ft fence: 8-ft posts with 2-3 ft in ground. |
| Rails | 2×4 | 2 rails up to 5 ft high, 3 rails for a 6 ft fence |
| Pickets | 1×4 or 1×6 | Actual face width 3.5 in or 5.5 in, not 4 in and 6 in |
| Concrete | 2 × 80 lb bags per post | 3 bags for posts over 6 ft or in soft ground |
Post depth matters more than post size. A post hole should be at least one third of the post's total length, with a few inches of gravel at the bottom for drainage so the post end does not stand in water and rot.
| Style | Gap between pickets | Effect |
|---|---|---|
| Privacy | 0–⅛ in | Solid screen; boards still need a hairline gap for expansion and drainage |
| Shadowbox | ⅛–½ in | Alternating boards on both faces; private but lets air through |
| Semi-privacy | ½–1½ in | Light and airflow pass; not a visual screen |
| Picket / estate | 2–4 in | Decorative boundary, fully open |
Add roughly 10% to the picket count for cutting waste and defects. Pickets break or come badly milled often enough that ordering the exact count guarantees a second trip.
| 3–4 ft | Decorative boundary |
| 4–5 ft | Pool fencing, local code often mandates height and self-closing gates |
| 5–6 ft | Pet containment, most dogs |
| 6 ft | Privacy, the most common residential fence |
| 7–8 ft | Tall privacy or noise abatement; 6×6 posts |
The post, section, rail and picket formulas follow the standard fence take-off method published by lumber and fencing suppliers, 8-foot post spacing as the residential default, one end post added to the bay count, two posts per gate, and picket counts derived from the actual face width of the board plus the gap. Post depth guidance follows the common 1/3-of-length rule and local frost-depth requirements. Always confirm fence height and setback against your local code and any homeowners' association rules.
Divide the total run by the post spacing and round up, then add one end post, and add two more posts for every gate. A 100 ft run at 8 ft spacing needs ⌈100÷8⌉ + 1 = 14 posts, plus two for each gate.
8 feet on centre is the residential default for a wooden board or privacy fence. Dropping to 6 feet makes the fence noticeably stiffer and is common in high-wind areas; it also raises the post count and the cost.
Multiply the run in inches by 12, subtract the gate openings, and divide by the picket's actual face width plus the gap. A 100 ft privacy run with 5.5 in pickets and no gap needs about 219 pickets; add 10% for waste.
Two 80 lb bags per post is the standard assumption for a typical 8–10 inch hole about 24–30 inches deep. Use three bags for posts taller than 6 feet, for gate and corner posts, or where the ground is soft.
Actual. A 1×6 board is 5.5 inches wide and a 1×4 is 3.5 inches. Using the nominal 6 or 4 in the arithmetic will under-count the pickets you need and leave you short.