Privacy Fence Calculator
Adjust the parameters below to compute materials and estimate project costs.
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Breakdown Details
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Guidelines & Field Recommendations
• Dig holes 24" to 30" deep (at least 1/3 of the post length).
• Post Hole diameter: 10-12 inches (3 times the post width).
• Concrete: Use 2 bags of 80lb concrete per post hole.
Calculation Formulas & Steps
Posts = (Perimeter ÷ Spacing) + 1. Rails = (Perimeter ÷ 8) × 3 (top, middle, bottom rails). Pickets = (Perimeter × 12) ÷ (Picket Width + Spacing). Concrete = 2 bags per post.
Worked Example (Step-by-Step Math)
Divide total length by post spacing, add 1 for final corner.
Posts = (150 ÷ 8) + 1 = 19.75 ≈ 20 postsStandard panel uses 3 rails (top, middle, bottom).
Rails = 150 ft ÷ 8 ft panels × 3 = 57 rails (8ft boards)Convert perimeter to inches, divide by picket width + spacing.
Pickets = (150 × 12) ÷ 5.5 = 328 pickets (+10% waste = 361)Fence Post Hole Guidelines
Proper post anchoring depths.
| Project Condition | Reference Metric |
|---|---|
| 6ft Fence Height | Dig holes 24" to 30" deep (1/3 of total post length) |
| Hole Diameter | 3x the post width (e.g. 12" diameter hole for 4x4 post) |
Critical Mistakes to Avoid
- !Mistake 1: Setting posts in dirt instead of concrete, causing the fence to lean within 2-3 years.
- !Mistake 2: Putting pickets tight against the grass, trapping moisture and rotting the wood.
Frequently Asked Questions
How many bags of concrete do I need per fence post hole?
For standard 4x4 fence posts, we recommend using exactly two (2) bags of 80 lb concrete per post hole. This provides a solid concrete collar that extends 24" deep, anchoring the post securely against wind loads and preventing rotational shifting.
What is the recommended picket spacing gap for a privacy fence?
A full privacy fence has a picket spacing gap of 0 inches. However, wooden pickets shrink slightly as they dry. Wood pickets installed touching edge-to-edge will shrink to create a 1/8" to 1/4" natural gap within 6 months.
Should I buy pre-assembled fence panels or build the fence from scratch?
Pre-assembled 8-foot fence panels are faster to install but can only be used on flat ground. If your yard has a slope, you must build the fence from scratch using individual pickets to run the fence stepped or racked along the ground contour.
How far apart should horizontal fence rails be spaced?
A standard 6-foot privacy fence requires three (3) horizontal 2x4 rails between posts: one placed 6-8 inches from the top, one in the middle, and one 6-8 inches from the ground to prevent pickets from warping.
How many individual fence pickets do I need for a 100-foot fence?
For 100 feet of fence using standard 5.5-inch wide pickets installed edge-to-edge: 100 × 12 = 1,200 inches. 1,200 ÷ 5.5 = 218 pickets. Add 10% for waste, requiring 240 pickets total.
Should I use pressure-treated lumber for fence posts?
Yes. Any wood touching the ground must be pressure-treated or cedar to resist moisture rot.
How high can a backyard privacy fence be without a permit?
In most municipalities, you can build a backyard privacy fence up to 6 feet tall without a permit. Front yard fences are usually limited to 3 or 4 feet.
Complete Tools Checklist
- Post Hole Digger
- String Line
- Level
- Nail Gun
- Hammer