Math July 13, 2026 · 8 Min Read

Post Spacing Calculator – Guide & Formulas

Calculate equal spacing intervals for fence posts, deck footings, or baluster supports over a total span.

Determine even spacing distances and layouts for fence posts, structural columns, deck piers, or railing balusters. Eliminate guesswork with fractional inches or metric coordinates.

Key Takeaway

Use the free Post Spacing Calculator to calculate equal spacing intervals for fence posts, deck footings, or baluster supports over a total span. Get instant results with step-by-step explanations.

How to Use the Post Spacing Calculator

  1. Enter the total length of the section or run.
  2. Input the desired or maximum allowed distance between posts.
  3. Specify individual post width to compute true clear spacings between elements.

The Formula

Sections = ceil(TotalLength / MaxSpacing) | ActualSpacing = (TotalLength - (PostCount * PostWidth)) / (PostCount - 1)

Variable Definitions

  • L_total: Total distance of fence or structural line
  • W_post: Thickness or diameter of each support post
  • N: Number of posts or sections

Spacing Posts for a 68-Foot Fence

Calculate post placement for a 68-foot long straight fence line using 4-inch square posts (3.5" actual size), aiming for roughly 8-foot intervals.

  1. Step 1: Set Total Length = 68 feet (816 inches) and max spacing of 8 feet (96 inches).
  2. Step 2: Find estimated sections: 68 ft / 8 ft = 8.5 sections. Round up to 9 sections.
  3. Step 3: Posts required: 9 sections + 1 terminal post = 10 posts.
  4. Step 4: Total width of posts: 10 × 3.5 in = 35 inches. Net space remaining: 816 - 35 = 781 inches.
  5. Step 5: Divide space by sections: 781 / 9 = 86.78 inches (approx. 7 feet 2-3/4 inches) clear distance between posts.

Frequently Asked Questions

Is it better to space fence posts closer or further apart?

Standard spacing is 6 to 8 feet. Closer spacing (6 feet) provides higher wind resistance and durability, while wider spacing (8 feet) saves on posts, concrete, and installation labor.

How deep should fence or deck posts be buried?

Posts should generally be buried at least one-third of their total height, and always below your local winter frost line to prevent shifting (usually 36" to 48" deep).

Does this calculator support corner posts?

Yes. It calculates straight lines, but you can subdivide your project into individual straight walls or runs between corner terminals.