Fence Calculator Formula
Understand the math behind the fence calculator. Each variable explained with a worked example.
Formulas Used
Posts Needed
num_posts = num_sections + 1Rails Needed
num_rails = fence_height > 6 ? num_sections * 3 : num_sections * 2Pickets Needed
num_pickets = ceil(total_length * 12 / picket_width)Variables
| Variable | Description | Default |
|---|---|---|
total_length | Total Fence Length(ft) | 100 |
fence_height | Fence Height(ft) | 6 |
post_spacing | Post Spacing(ft) | 8 |
picket_width | Picket Width(in) | 3.5 |
num_sections | Derived value= ceil(total_length / post_spacing) | calculated |
How It Works
Fence Calculation
Posts = (Total Length / Post Spacing) + 1
Rails = Sections × Rails per Section (2 for fences ≤6ft, 3 for taller)
Pickets = Total Length (in) / Picket Width
Add 10% for waste.
Worked Example
100 ft fence, 6 ft tall, 8 ft spacing, 3.5 in pickets.
- 01Sections = ceil(100/8) = 13
- 02Posts = 13 + 1 = 14
- 03Rails = 13 × 2 = 26
- 04Pickets = ceil(1200 / 3.5) = 343
Frequently Asked Questions
How deep should fence posts be set?
Posts should be buried 1/3 of their total length. For a 6ft fence, use 8ft posts buried 2ft deep in concrete.
How far apart should fence posts be?
6 to 8 feet is standard. Closer spacing (6ft) provides more strength; 8ft is the maximum recommended distance.
Learn More
Guide
How to Calculate Fence Materials
Learn how to calculate fence materials including posts, rails, pickets, and concrete for any fence length and style. Proper material estimates prevent project delays and reduce leftover waste.
Ready to run the numbers?
Open Fence Calculator