How this calculation works
The Fence Materials Calculator estimates the number of support posts, horizontal 2x4 rails, vertical pickets, and bags of fast-setting concrete required to build a wood or vinyl fence.
Mathematical formula and logic
Sections = ceil(Linear Feet / Post Spacing). Posts = Sections + 1 + Gates. Rails = Sections × (Height >= 6 ? 3 : 2). Pickets (5.5 in) = (Linear Feet × 12) / 5.5.
Worked example
For a 150 linear foot fence with 8 ft post spacing, 6 ft height, and 1 gate: You need 19 sections, 21 posts (4x4), 57 rails (2x4), approximately 328 pickets, and 42 bags of concrete (2 bags/post).
Calculation assumptions
- Fences 6 ft or taller require 3 horizontal 2x4 rails per section; fences under 6 ft require 2 rails.
- Each support post requires two 50 lb bags of fast-setting concrete for standard 24-36 inch hole depth.
Frequently asked questions
How deep should fence posts be buried in the ground?
As a general rule, 1/3 of the total post length should be buried in the ground (e.g. an 8 ft post for a 6 ft fence should be buried 2 ft / 24 inches deep, below the local frost line).
How many bags of concrete do I need per fence post?
Most residential fence installations require 1.5 to 2 fifty-pound (50 lb) bags of fast-setting concrete per 4x4 post hole.
Why is 8-foot post spacing standard?
Lumber rails (2x4s) are standardly sold in 8-foot lengths. Spacing posts 8 feet on center minimizes waste and structural deflection.
What type of wood is best for fence posts?
Pressure-treated pine (rated for ground contact UC4A) or naturally rot-resistant Western Red Cedar are the most durable wood options.
How many pickets are needed per foot of fence?
Standard 5.5-inch dog-ear pickets require approximately 2.2 pickets per linear foot with zero gap, or 2.1 pickets with a small 1/8-inch seasonal expansion gap.