Before building a fence, you need to plan the materials – and that starts with getting the length calculation right. Buy too little and you'll run out of fence panels mid-project. Order too much and you're dealing with expensive returns or leftover materials. Simply measuring the perimeter isn't enough: gates must be subtracted, post spacing must be optimised and the number of posts must be calculated. The fence length calculator handles all this planning and outputs a complete materials list.
Step by Step: How to Use the Fence Length Calculator
- Choose plot shape: Select rectangular, square, L-shaped or enter the perimeter directly.
- Enter dimensions: For a rectangular plot: length and width in meters – e.g. 25 m × 18 m.
- Enter gates and driveways: Enter the total width of all gates, e.g. 1 garden gate (1.2 m) + 1 driveway gate (3.5 m) = 4.7 m. This figure is deducted from the perimeter.
- Enter post spacing: Standard post spacing: 1.5–2.0 m for metal fencing, 1.8–2.5 m for wooden fencing.
- Read the result: The calculator outputs total length, fence length excluding gates, number of posts and number of fence panels.
Practical Examples
Example 1 – Terraced house garden: Plot 20 m × 12 m, perimeter: 2 × (20 + 12) = 64 m. Deduct 1 garden gate (1.2 m) and 1 driveway opening (2.8 m): 64 – 4.0 = 60 m of fencing. At 2.0 m post spacing: 60 ÷ 2.0 = 30 fence panels + 31 posts (always number of panels + 1).
Example 2 – Round garden pond enclosure: Circular enclosure with 3 m radius. Perimeter = 2 × π × 3 = 18.85 m. At 1.5 m post spacing: about 13 panels and 13 posts (for a circle, the last panel connects back to the first post).
Example 3 – Horse paddock: L-shaped paddock: 30 m long, 20 m wide, but one corner of 10 m × 10 m is missing. Perimeter: (30 + 20 + 20 + 10 + 10 + 10) = 100 m. At 3.0 m post spacing: 34 panels, 34 posts. Plus 2 × 3 m field gates for paddock access.
Fence Length Calculation: Plot, Posts and Gates
For a 20×15 m plot: perimeter = 2×(20+15) = 70 m. At 1.8 m post spacing = 39 posts required.
Frequently Asked Questions (FAQ)
- How many posts do I need for a given fence length?
- The formula is: number of posts = (fence length ÷ post spacing) + 1. For 60 m of fence at 2 m spacing: 60 ÷ 2 + 1 = 31 posts. At every corner and beside every gate, you need additional structural posts – plan at least one extra post per corner.
- What post spacing is recommended for different fence types?
- Welded mesh panels: 2.0 m standard, posts concreted in. Wooden slat fencing: 1.5–1.8 m. Post-and-rail paddock fencing: 2.5–3.0 m with driven posts. Privacy screens (wind load): 1.5 m maximum due to the large surface area. In very soft or sandy ground, reduce spacing by 20%.
- What do I need to consider when planning gates?
- Gates need gate posts on both sides that are more solidly founded than standard fence posts (larger concrete base, greater embedment depth). Allow at least 10 cm more width per gate leaf than the clear opening – for a 1.0 m clear passage, use a 1.10 m wide gate pair (2 × 55 cm leaves).
