Electric Fence Calculator
Calculate the wire, posts and energizer rating needed for an electric fence.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
Estimate total wire length and post count from the perimeter, strand count and post spacing. These quantities do not determine the right energizer: follow the energizer maker’s guidance for fence condition, vegetation, grounding and the animals being controlled, then test voltage along the installed fence.
Worked example
calculated with the default values below
Fence perimeter 800 ft · Number of strands 3 · Post spacing 12 ft Total wire needed 2,400 ft · Posts needed 68 · Fence length 0.152 mi
Method and assumptions
W = P × S; N = ceil(P ÷ d) + 1; M = P ÷ 5280 Wire length = perimeter × strands; posts = ceil(perimeter ÷ post spacing) + 1; perimeter in miles = perimeter ÷ 5280. These outputs do not size an energizer; use manufacturer guidance and test the installed fence. Estimate total wire length and post count from the perimeter, strand count and post spacing. These quantities do not determine the right energizer: follow the energizer maker’s guidance for fence condition, vegetation, grounding and the animals being controlled, then test voltage along the installed fence. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Data sources
Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
W = P × S; N = ceil(P ÷ d) + 1; M = P ÷ 5280
- P
- fence perimeter (ft)
- S
- wire strands
- d
- post spacing (ft)
- W
- total wire length (ft)
- N
- estimated posts
- M
- perimeter (miles)
Wire length = perimeter × strands; posts = ceil(perimeter ÷ post spacing) + 1; perimeter in miles = perimeter ÷ 5280. These outputs do not size an energizer; use manufacturer guidance and test the installed fence.
Frequently asked questions
How should I choose an energizer?
Estimate total wire length and post count from the perimeter, strand count and post spacing. These quantities do not determine the right energizer: follow the energizer maker’s guidance for fence condition, vegetation, grounding and the animals being controlled, then test voltage along the installed fence.
Which inputs and limits apply to Electric Fence Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Fence perimeter: 10–50,000 ft; Number of strands: 1–12; Post spacing: 4–60 ft W = P × S; N = ceil(P ÷ d) + 1; M = P ÷ 5280 Wire length = perimeter × strands; posts = ceil(perimeter ÷ post spacing) + 1; perimeter in miles = perimeter ÷ 5280. These outputs do not size an energizer; use manufacturer guidance and test the installed fence. Estimate total wire length and post count from the perimeter, strand count and post spacing. These quantities do not determine the right energizer: follow the energizer maker’s guidance for fence condition, vegetation, grounding and the animals being controlled, then test voltage along the installed fence. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
What is a complete worked example for Fence perimeter = 800 ft; Number of strands = 3?
Inputs: Fence perimeter = 800 ft; Number of strands = 3; Post spacing = 12 ft. Calculation: W = P × S; N = ceil(P ÷ d) + 1; M = P ÷ 5280. Results: Total wire needed = 2,400 ft; Posts needed = 68; Fence length = 0.152 mi.