Fence Calculator
Calculate the number of posts, rails, and pickets needed for a fence based on length and spacing.
This free online fence calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.
Minimum: 0
Total length of the fence line
Distance between posts (6-8 ft typical)
Horizontal rails per section (2 or 3)
Minimum: 0
Width of each picket in inches
Space between pickets
Results
Posts
13
Rails
24
Pickets
229
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Fence Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Fence Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
Formula Reference
Fence Calculator Formula
See calculator inputs for the governing equation
Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.
When to Use This Calculator
- •Use the Fence Calculator when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
- •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
- •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
- •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.
About This Calculator
The Fence Calculator is a free, browser-based calculation tool for engineers, students, and technical professionals. Calculate the number of posts, rails, and pickets needed for a fence based on length and spacing. It implements standard formulas and supports both metric (SI) and imperial unit systems with automatic unit conversion. All calculations are performed instantly in your browser with no data sent to a server. Use this calculator as a quick reference and sanity-check tool during design, analysis, and learning. Always verify results against primary engineering references and applicable standards for any safety-critical application.
About Fence Calculator
Building a fence requires careful planning to determine the number of posts, rails, and pickets. Post spacing depends on the fence style and wind load -- 6 to 8 feet is standard for most residential fences. Rails connect the posts horizontally, and pickets (or boards) are attached vertically to the rails. This calculator provides a material list based on your fence length, post spacing, and picket dimensions. Whether you are building a privacy fence, a picket fence, or a ranch-style fence, getting accurate counts ensures you make one trip to the lumber yard instead of three.
The Math Behind It
Formula Reference
Posts
Posts = floor(Length / Spacing) + 1
Variables: Length and spacing in feet
Pickets
Pickets = Fence Length (in) / (Picket Width + Gap)
Variables: All in inches
Worked Examples
Example 1: 100 ft privacy fence, 8 ft post spacing
Length = 100 ft, Spacing = 8 ft, Rails = 3, Picket = 5.5 in, Gap = 0 in
You need 13 posts, 36 rails, and 219 fence boards.
Common Mistakes & Tips
- !Forgetting the +1 for the end post (a 100 ft fence with 10 ft spacing needs 11 posts, not 10).
- !Not accounting for gate openings which require wider spacing and additional hardware.
- !Using untreated lumber for in-ground posts, leading to premature rot.
- !Setting posts too shallow in cold climates where frost heave is a concern.
Related Concepts
Used in These Calculators
Calculators that build on or apply the concepts from this page:
Frequently Asked Questions
How deep should fence posts be set?
As a rule of thumb, bury one-third of the total post length. For a 6-foot fence with 8-foot posts, set them 24-30 inches deep, or deeper if below the frost line in your area.
What post spacing should I use?
Most residential fences use 6 to 8 foot spacing. Use 6 feet for areas with high winds or for tall fences, and 8 feet for standard conditions with shorter fences.