How to Calculate Fencing Materials: Posts, Rails and Panels

How to Calculate Fence Materials

Calculating fence materials accurately prevents costly trips back to the lumber yard. The three main components to estimate are posts, panels (or rails + pickets), and hardware.

Step 1: Calculate Total Fence Length

Measure the perimeter you're fencing (or the linear footage of fence line).

Example: Backyard fence, 120 linear feet total.

Step 2: Calculate Number of Posts

Number of posts = (Total length / Post spacing) + 1

For 8-foot post spacing: 120 / 8 = 15 + 1 = 16 posts

Add posts for each corner: +4 corners (may already be included in the above count if corners fall on 8-ft intervals)

Step 3: Calculate Panels or Pickets

If using pre-built 8-ft panels: 120 ft / 8 ft per panel = 15 panels

If building with pickets:

Number of pickets = Total length / (Picket width + Gap width)

For 3.5-inch pickets with 0.5-inch gaps: 120 ft × 12 in/ft / (3.5 + 0.5) = 1,440 / 4 = 360 pickets

Step 4: Rails (for Picket Fences)

Most 4–6 ft fences use 2 horizontal rails per bay; 6+ ft fences use 3. Rails per bay × Number of bays = Total rails 2 rails × 15 bays = 30 rails (each 8 ft long)

Post Depth Rule of Thumb

Posts should be buried 1/3 to 1/2 their total length. For a 6-ft fence with 8-ft posts, bury 2 ft (leaving 6 ft above ground).

Use our fence calculator for any perimeter and style.