Fence Calculator
Calculate exactly how many posts, rails, and pickets you need for your fence project. Enter linear footage and fence style to get complete material list with concrete quantities.
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Enter your values above to see the results.
Tips & Notes
- ✓Dig post holes 6 inches below the frost line for your region, not to the frost line — the extra depth provides a margin that prevents heaving even in unusually cold winters.
- ✓Set corner posts and gate posts first, then stretch a string line between them to align intermediate posts precisely — this is faster and more accurate than measuring each intermediate post individually.
- ✓Use pressure-treated lumber rated for ground contact (UC4B rating) for all posts — standard pressure-treated lumber rated only for above-ground use (UC3) deteriorates in 3–7 years when buried.
- ✓Let concrete set for 48 hours before attaching rails and pickets — loading a freshly poured post before the concrete cures fully can shift the post out of plumb permanently.
- ✓Pre-stain or pre-paint fence boards before installation for complete coverage — painting after assembly leaves the end grain and back face unpainted, accelerating weathering and shortening the fence lifespan.
Common Mistakes
- ✗Setting posts at equal spacing without accounting for corners and gate openings — corner posts and gate posts interrupt the regular spacing rhythm and must be placed first to set the layout.
- ✗Using the same post hole depth for all fence heights — taller fences and gate posts carry significantly more lateral load and require deeper, larger-diameter holes with more concrete.
- ✗Choosing standard (above-ground) pressure-treated lumber for in-ground posts — this is one of the most common fence failures and causes post rot within 5–10 years regardless of climate.
- ✗Installing fence rails with the flat side horizontal instead of the edge facing up — rails installed flat-side-horizontal collect water in the center, accelerating rot at exactly the point where pickets are attached.
- ✗Not allowing for gate swing clearance — a 4-foot gate opening requires approximately 48 inches of clear horizontal space when fully open, which may overlap with another fence section or adjacent structure.
Fence Calculator Overview
Fence material estimation requires calculating linear footage of fence run, converting that to post count, rail count, and picket or panel count based on your chosen spacing and fence style. Under-ordering means a mid-project trip back to the supplier where boards may not match in grain or color; over-ordering creates waste on lumber that rarely has resale value. Accurate calculation prevents both problems.
Post count formula:
Number of Posts = (Total Linear Feet ÷ Post Spacing) + 1 per straight run
EX: 120 ft fence with posts every 8 ft → 120 ÷ 8 = 15 sections + 1 post = 16 posts. Add corner posts: +2. Add gate posts: +2 per gate opening. Total posts: 20 for a 120 ft fence with 2 corners and 1 gateMaterial requirements by fence style:
| Fence Style | Posts | Rails per Section | Pickets/Boards per 8 ft Section | Typical Height |
|---|---|---|---|---|
| Privacy (dog-ear board) | Every 8 ft | 2–3 horizontal rails | 13–16 pickets (6 in wide) | 6 ft |
| Picket fence (decorative) | Every 6–8 ft | 2 rails | 12–15 pickets (3.5 in wide) | 3–4 ft |
| Split rail | Every 8–10 ft | 2–3 split rails | N/A (open style) | 3–4 ft |
| Chain-link (6 ft) | Every 10 ft | 1 top rail | Chain-link fabric by linear ft | 4–6 ft |
| Shadowbox | Every 8 ft | 3 rails | 24–28 pickets (alternating sides) | 6 ft |
| Fence Height | Post Size | Hole Depth | Hole Diameter | Concrete per Post |
|---|---|---|---|---|
| 3–4 ft | 4×4 in | 24 in (below frost line) | 8–10 in | ½ bag (40 lb) |
| 5–6 ft | 4×4 in | 36 in (below frost line) | 10–12 in | 1 bag (60 lb) |
| 6–8 ft | 6×6 in | 42–48 in | 12 in | 1.5 bags (80 lb each) |
| Gate posts | 6×6 in | 48 in minimum | 12–16 in | 2 bags (60 lb each) |
Frequently Asked Questions
With 8-foot post spacing: 100 ÷ 8 = 12.5 sections, round up to 13 sections, plus 1 end post = 14 posts for a straight run. Add posts for corners and gate openings: each 90-degree corner adds 1 post, each gate opening adds 2 posts. A 100-foot fence with 2 corners and 1 gate requires approximately 14 + 2 + 2 = 18 posts. Always plan post locations before purchasing — the layout determines the exact count.
The standard rule: set posts at least one-third of the total post length in the ground, and always below the local frost line. For a 6-foot fence using 9-foot posts: set 3 feet in ground, leaving 6 feet above grade. In regions with 36-inch frost lines (northern US), this requires 9-foot posts minimum. Contact your local building department for the frost depth in your area — this is the single most important structural requirement for fence longevity.
Cedar and redwood are naturally rot-resistant and are the premium choice for wood fences — they last 15–20+ years without treatment and accept stain beautifully. Pressure-treated pine is the most economical choice and lasts 10–15 years when properly maintained. For posts (in-ground): always use pressure-treated lumber rated UC4B for ground contact, regardless of what material you choose for rails and pickets. Avoid Douglas fir and spruce for fence boards — they absorb moisture readily and deteriorate quickly.
In most US jurisdictions, yes for fences over 6 feet tall and sometimes for fences of any height in front yards. Permit requirements vary by municipality — some require permits for any fence regardless of height, others only for fences above 4 or 6 feet. Always check with your local building department before starting. Additionally, verify property line location before installing — encroaching even 6 inches into a neighbor property creates legal liability that can require removing and rebuilding the entire fence.
Standard recommendation: one 60 lb bag of concrete per 4×4 post in a 10-inch diameter hole, and two 60 lb bags per 6×6 post or gate post in a 12-inch hole. For 20 standard posts and 4 gate posts: 20 × 1 bag + 4 × 2 bags = 28 bags of 60 lb concrete. Fast-setting concrete (like Quikrete Fast-Setting) does not require mixing — pour dry into the hole and add water on top. It achieves working strength in 4 hours vs. 24–48 hours for standard concrete.
Properly installed and maintained cedar or redwood fences last 15–20 years. Pressure-treated pine fences last 10–15 years. Untreated softwood fences last 5–10 years. The biggest factors in fence lifespan are: post material and depth (the most critical), whether rails are properly sloped to shed water, whether the fence receives periodic staining or sealing (every 2–3 years extends life significantly), and whether the fence bottom has clearance above grade (contact with soil accelerates rot).