A useful fence material estimate starts with the total run length and planned post spacing. From there, you can calculate the number of bays, horizontal rails and pickets, then estimate concrete for identical post holes. This guide focuses on a single straight fence run.
1. Calculate the number of posts
Divide the fence length by the maximum post spacing and round up, then add one post for the opposite end:
Posts = round up (fence length ÷ post spacing) + 1
For a 100-foot straight run at 8-foot spacing, round up 100 ÷ 8 to 13 spaces, then add one: 14 posts. The result assumes a straight, uninterrupted line and evenly spaced posts.
2. Estimate rails and pickets
The number of bays is the number of posts minus one. Multiply bays by the number of horizontal rails required per bay. For pickets, divide fence length in inches by the combined face width and gap, round up, and add a waste allowance.
3. Estimate concrete for post holes
For a cylindrical hole, volume in cubic feet equals π multiplied by the square of the hole radius in feet, multiplied by the hole depth in feet. Multiply by the number of posts, then divide by the yield per concrete bag and round up.
Hole volume = π × radius² × depth
Use the Calclio Fence Calculator to estimate posts, bays, rails, pickets and bagged concrete, with optional unit prices.
Important layout considerations
- Corner posts, gate openings, end posts, slopes and step-downs change the layout.
- Post spacing and hole depth depend on fence height, wind exposure, soil, material and local rules.
- Gate hardware and reinforced gate posts are not included in this straight-run estimate.
- Confirm concrete bag yield from the manufacturer’s label and do not assume every product fills the same volume.
- Check property boundaries, underground utilities and required permits before digging.
Frequently asked questions
How many posts do I need for 100 feet of fence?
At 8-foot spacing, the simple straight-line estimate is 14 posts. Corners and gates can change the count.
How many rails should a fence have?
It depends on fence height, board design and the material manufacturer’s recommendations. Enter the rail count specified in your plan.
Does this calculator include gates?
No. Estimate gate widths, hardware and reinforced gate posts separately.
Related tools: Deck Material Calculator · Concrete Slab Calculator · Gravel Calculator.