Fence Calculator: Posts, Rails, Pickets & Concrete Estimator
Use this fence calculator to estimate materials for privacy and picket fences. Computes total line, corner, and end posts, horizontal support rails, pickets with spacing gaps, and concrete bags per post hole.
Buy 15 posts (4×4), 36 horizontal rails (2×4), 218 vertical pickets (6 ft tall), and 23 bags of fast-setting concrete for post footings.
| Total Fence Run (minus 4 ft gate) | 96 linear ft |
|---|---|
| Fence Sections (8 ft spacing) | 12 sections |
| Fence Posts Required (with corners & ends) | 15 posts (4×4 timber) |
| Horizontal 2×4 Rails Needed | 36 rails (3 per section) |
| Vertical Pickets (5.5" width + 8% scrap) | 218 pickets |
| Fast-Setting Concrete Bags (50 lb) | 23 bags (1.5 bags/post) |
📐 Show Formula and Default Assumptions
We believe all home improvement estimates should be transparent and verifiable. Below is the exact math running in this browser tool:
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Fence Post Count:
Sections = ceil( Net Fence Length ÷ Post Spacing ) | Posts = Sections + 1Calculates continuous line posts plus end closure post. -
Picket Quantity:
Pickets = (Net Fence Length in) ÷ (Picket Width in + Gap in)Incorporates spacing gaps between pickets for privacy vs shadowbox styles. -
Post Hole Concrete:
Total Concrete = Post Count × Bags per Post (default 1.5 bags of 50 lb mix)Standard rule: 1/3 of post buried in ground set with 1.5 to 2 bags of fast-setting concrete.
Note: All default assumptions (waste %, coverage rates, container yields) can be adjusted directly in the input fields above to match your project specifications.
How to Measure and Stake Your Property for Fencing
- Locate your exact boundary pins: Never guess property lines. Locate metal survey pins or hire a surveyor before installing permanent fence posts.
- Call 811 before digging: Always call utility locating services to mark underground power, gas, and fiber optic lines.
- Drive stakes at corners and pull string: Run tight mason string 6 inches above ground from corner to corner to establish straight fence lines.
- Deduct gate openings: Measure proposed gate widths (e.g. 4 ft for walking gates, 10 ft for double lawnmower gates) and deduct from picket runs.
- Mark post locations: Measure 8-foot intervals along the string line. On uneven terrain, reduce spacing to 6 feet to handle slope changes smoothly.
- Add gravel drainage to post holes: Before pouring concrete around a wooden fence post, dump 4 to 6 inches of coarse drainage gravel into the bottom of the augered hole. This allows water entering from above to drain freely into subsoil rather than soaking the bottom end-grain of the post, preventing ground rot.
- Dome concrete collars above grade: When finishing wet concrete around fence posts, trowel the top surface into a gentle cone or dome shape rising 1 inch above surrounding lawn level. This sheds rainwater outward away from the wood post rather than forming a concave puddle basin that accelerates rot.
How the Fence Calculation Works (Worked Example)
Consider a 100-foot run of 6-foot tall wood privacy fence with one 4-foot walking gate, 8-foot post spacing, 3 horizontal rails, and 5.5" pickets:
- 1. Net Fence Length: 100 ft total - 4 ft gate = 96 ft of picketed run.
- 2. Number of Sections: 96 ft ÷ 8 ft spacing = 12 sections.
- 3. Total Posts Needed: 12 sections + 1 end post = 13 posts (4x4 × 8 ft pressure treated).
- 4. Horizontal Rails (3 rails per section): 12 sections × 3 rails = 36 rails (2x4 × 8 ft).
- 5. Pickets Needed (5.5" wide, 0" gap): 96 ft = 1,152 inches. 1,152 ÷ 5.5 = 209.4 pickets.
- 6. 8% Picket Waste & Sorting: 209.4 × 1.08 = 226 pickets (1x6 × 6 ft dog-ear cedar or pine).
- 7. Concrete Required: 13 posts × 1.5 bags/post = 19.5 -> 20 bags of 50 lb fast-setting concrete.
Fencing Heights, Post Lengths & Depth Guidelines
| Fence Height | Recommended Post Length | Hole Depth (In Ground) | Rails Per Section |
|---|---|---|---|
| 3 ft - 4 ft (Picket) | 6 ft Post (4x4) | 24 Inches (60 cm) | 2 Rails (2x4) |
| 5 ft (Privacy/Pool) | 7 ft or 8 ft Post (4x4) | 30 Inches (75 cm) | 2 to 3 Rails (2x4) |
| 6 ft (Standard Privacy) | 8 ft Post (4x4) | 32 - 36 Inches (80-90 cm) | 3 Rails (2x4) |
| 8 ft (Commercial/Sound) | 10 ft or 12 ft Post (4x6 or 6x6) | 42 - 48 Inches (105-120 cm) | 4 Rails (2x4) |
Frequently Asked Questions About Fence Calculator
How deep should fence post holes be dug?
A fence post hole should be dug to a depth equal to 1/3 to 1/2 of the above-ground fence height (e.g., a 6-foot fence needs a hole 30" to 36" deep). The hole width should be 3 times the diameter of the post (e.g. 10" to 12" wide for a 4x4 post).
How many horizontal rails are needed on a 6-foot privacy fence?
A 6-foot privacy fence always requires 3 horizontal 2x4 rails per 8-foot section (top, middle, and bottom). Using only 2 rails allows 6-foot pickets to warp, bow, and cup under summer heat and winter moisture.
Should I use fast-setting concrete or standard concrete for fence posts?
Fast-setting concrete (like Quikrete Fast-Set in the red bag) is the industry standard for post setting. You pour the dry powder straight into the hole around the plumb post and add water; it sets in 20 to 40 minutes with no trough mixing required.
Why is 8 feet the standard spacing between fence posts?
Dimensional framing lumber for horizontal rails is sold standard in 8-foot lengths. Spacing posts wider than 8 feet causes rails to sag under the weight of pickets and dramatically reduces wind resistance.
What type of fasteners should be used for cedar pickets?
Use hot-dipped galvanized ring-shank nails or stainless steel screws. Never use standard zinc-plated or interior drywall screws; the natural tannins in cedar and pressure-treated wood will corrode them, creating black streak stains within months.
Should I attach fence rails with screws or framing nails?
Always use 3-inch or 3-1/2-inch exterior ceramic-coated or stainless steel star-drive (Torx) screws rather than smooth nails. Nails pull loose over time under wind shear and seasonal lumber expansion, whereas structural exterior screws provide permanent pull-out resistance.