Free calculator
Fence Calculator: Posts, Pickets, Rails & Concrete
Measure your run in linear feet and get a complete wood-fence material list: posts and sections, pickets, horizontal rails, gate posts, and the concrete per hole — with hole volume minus post displacement, so the bag count is honest. Everything is rounded up and the arithmetic is shown in full.
By HowMuchBuild Editorial TeamCalculation reviewedUpdated October 2026
linear feet — measure the whole run
feet — 8 ft is typical
number of gate openings
Post holes (for concrete)
inches — 12″ is typical
inches — go below the frost line
We use actual lumber dimensions so the post displacement is accurate.
Estimated cost
What will it cost?
Enter your local store prices — prices vary by region.
Fence posts
16 posts
—
Pickets
219 pickets
—
Rails
39 rails
—
80-lb concrete bags
57 bags
—
Estimate — prices vary by store and region. Check your local store for current pricing.
Material takeoff
16
posts (14 line + 2 gate)
219
pickets
39
rails (3/section)
57
80-lb bags of concrete
Every count is rounded up. Concrete is per 12″-diameter hole minus post displacement; adjust hole size to match your dig.
13
sections · ≈ 7.69 ft apart
312
linear ft of 2×4 rails
How we calculated it
- Sections = ⌈100 ft ÷ 8 ft⌉ = 13 (actual spacing ≈ 7.69 ft)
- Posts = 13 + 1 line posts = 14, plus 1 × 2 gate posts = 2 → 16 total
- Pickets (privacy) = ⌈1200″ ÷ 5.5″ coverage⌉ = 219
- Rails = 13 sections × 3 (6 ft fence, typical) = 39 rails × 8 ft = 312.0 lin ft
- Concrete/post = 2.36 (hole) − 0.26 (post) = 2.10 cu ft → ⌈2.10 ÷ 0.60⌉ = 4 × 80-lb bags
- Total concrete = 2.10 × 16 posts = 33.62 cu ft → 57 × 80-lb bags
Planning estimates — they don't include hardware, hinges, latches, or gate frames. Post depth should pass below your local frost line (a common rule of thumb is about one-third of the post's length below grade), and setback rules vary by municipality — check local code before you dig.
Worked example: 100 ft privacy fence, 6 ft tall
One straight 100-ft run, 8-ft post spacing, 1 gate, 12″-diameter holes 36″ deep, 4×4 posts:
- Sections: ⌈100 ÷ 8⌉ = 13 sections (posts land ≈ 7.69 ft apart: 100 ÷ 13)
- Posts: 13 + 1 = 14 line posts, plus 1 × 2 = 2 gate posts = 16 posts total
- Pickets: ⌈(100 × 12)″ ÷ 5.5″⌉ = ⌈218.18⌉ = 219 pickets
- Rails: 13 sections × 3 (6 ft fence, typical) = 39 rails → 39 × 8 = 312 lin ft of 2×4
- Concrete per post: hole π × 0.5² × 3 = 2.3562 cu ft; post (3.5 ÷ 12)² × 3 = 0.2552 cu ft; net 2.3562 − 0.2552 = 2.101 cu ft
- Bags: ⌈2.101 ÷ 0.60⌉ = 4 × 80-lb bags per post; total ⌈16 × 2.101 ÷ 0.60⌉ = 57 bags
Posts per 100 ft by spacing
| Post spacing | Line posts per 100 ft |
|---|---|
| 6 ft | 18 |
| 8 ft (typical) | 14 |
| 10 ft | 11 |
| 12 ft | 10 |
Pickets per 100 ft by style
| Style | Pickets per 100 ft |
|---|---|
| Privacy (no gap) | 219 |
| Spaced, 2″ gap | 160 |
| Spaced, 3.5″ gap | 134 |
80-lb bags per post (12″ dia × 36″ deep hole)
| Post size | Concrete per post | 80-lb bags (rounded up) |
|---|---|---|
| 4×4 (actual 3.5″) | 2.10 cu ft | 4 |
| 6×6 (actual 5.5″) | 1.73 cu ft | 3 |
The formulas
Sections and posts
Sections = ⌈ total feet ÷ post spacing ⌉; line posts = sections + 1; total posts = line posts + (gates × 2). Two extra posts per gate (one each side) is the typical allowance.
Pickets
Pickets = ⌈ (total feet × 12) ÷ 5.5″ ⌉ for privacy style — a 1×6 board covers 5.5″ of actual width. For spaced pickets: ⌈ (total feet × 12) ÷ (5.5″ + gap) ⌉.
Rails
Rails = sections × 2 for fences up to 4 ft, × 3 for 5–6 ft (typical). Each rail is one post-spacing long.
Concrete per post
V = hole volume − post volume. Round hole: π × r² × depth, minus the post's actual cross-section (a 4×4 is really 3.5″ × 3.5″) times depth. Bags = ⌈ V ÷ 0.60 ⌉ for 80-lb bags.
Frequently asked questions
How many fence posts do I need for 100 feet?
At the typical 8-ft post spacing, 100 linear feet gives ⌈100 ÷ 8⌉ = 13 sections and 14 line posts (one more than the number of sections). Add 2 posts per gate opening on top of that.
How many pickets do I need for a 100 ft privacy fence?
219. A nominal 1×6 picket covers 5.5″ of actual width, so ⌈1200″ ÷ 5.5″⌉ = 219 pickets for 100 linear feet with no gaps.
How many rails per fence section?
As a typical rule: 2 rails per section for fences up to 4 ft tall, 3 rails per section for 5–6 ft fences. Each rail runs the full section length between posts.
How much concrete do I need per fence post?
A 12″-diameter, 36″-deep hole holds 2.36 cu ft; a 4×4 post (actual 3.5″) displaces 0.26 cu ft, leaving 2.10 cu ft of concrete — that's 4 eighty-pound bags per post (0.60 cu ft each), always rounded up.
How deep should fence post holes be?
A common rule of thumb is about one-third of the post's total length below grade — so a 6-ft fence typically uses 8-ft posts set ~2 ft deep — but the hole must always pass below your local frost line. Frost depth varies by region, so confirm the minimum depth with local code.
Should I use 4×4 or 6×6 fence posts?
4×4 posts are the standard for most residential picket and privacy fences; 6×6 posts are the typical choice for taller fences, heavy double gates, and wind-exposed runs. Longer spans and taller fences may also need deeper holes — check local requirements.
Before you dig
Call your local utility-locating service (811 in most US states) before any post hole goes in the ground. Confirm property lines and setback rules with your municipality — many towns require permits or neighbor notification for fences, and height limits are common along sidewalks and corners. Hardware, hinges, latches, and gate frames aren't in the material list above, so budget for those separately.
Keep estimating