🪵 Fence Calculator

Fence Calculator - How to Estimate Posts, Pickets, Rails and Concrete for Any Fence

A fence project that runs short of materials mid-installation is one of the most frustrating and avoidable problems in home construction. Getting the quantities right before you order means no delays waiting for a second delivery, no mismatched material batches, and no overspend on excess stock you can't return. This calculator walks through every material type - posts, pickets, rails, panels, and concrete - for wood, chain-link, vinyl, and metal fences.

How to Calculate Fence Posts - The Formula

The post count depends on the total fence length, the post spacing, and whether you're fencing a closed perimeter (where the last post meets the first) or an open run (where you need an end post at each terminus).

For an open run: Number of posts = (Length ÷ Spacing) + 1. The "+1" accounts for the final end post. For a closed perimeter (going around all four sides): Number of posts = Perimeter ÷ Spacing (no "+1" because the last post is the first post).

Always round the bay count up - if your division gives 16.7 bays, that means 17 bays and 18 posts. You can slightly tighten the spacing to keep posts even, but never plan for a fractional bay. Gate posts are in addition to the calculated posts - add 2 per gate opening (one on each side).

Fence Post Depth - The One-Third Rule

The most common mistake in fence installation is setting posts too shallow. The standard rule: the buried depth should be one-third to one-half of the above-ground height. This prevents leaning under wind load and frost heave in colder climates.

• 1.2m above-ground fence → bury at least 0.4–0.6m (total post length: 1.6–1.8m)
• 1.8m above-ground fence → bury at least 0.6–0.9m (total post length: 2.4–2.7m)
• 2.4m above-ground fence → bury at least 0.8–1.2m (total post length: 3.2–3.6m)

Post holes should be approximately 3× the post diameter in width. Fill with concrete for all permanent fences - one 50kg bag of ready-mix concrete per standard residential post, two bags for taller or heavier structural posts. Allow 24–48 hours to cure before attaching rails or panels.

Fence Type Comparison - Cost, Maintenance and Lifespan

Post Spacing - What's Standard for Each Fence Type

Post spacing affects both material cost (more posts = more cost and concrete) and fence strength (closer posts = more rigid). Standard spacings:

• Wood privacy fence: 1.8m–2.4m spacing. Shorter spacing for taller fences (1.8m height or more) or high-wind areas.
• Chain-link: 2.4m–3.0m between line posts, with terminal posts (corner and end) always in concrete regardless of intermediate spacing.
• Vinyl panel: 2.4m is the standard - most vinyl panels are manufactured in 2.4m widths to match this spacing exactly.
• Metal railing: 1.8m–3.0m depending on rail height and structural requirement. Pool fencing typically requires closer spacing for compliance.

Gate Planning - What the Calculator Accounts For

Gates require special consideration in any fencing project. Each gate needs two dedicated gate posts - typically heavier gauge or larger diameter than line posts, set deeper in concrete to handle the swinging load. The gate opening width must be measured to the inside faces of the gate posts (not the outside of the posts), as this determines the actual clear opening.

Common gate widths: 900mm–1.2m for pedestrian gates; 2.4m–3.6m for vehicle gates. Double gates can span 3.6m–4.8m. In the perimeter calculator above, entering a gate subtracts the gate width from the total fencing material needed while adding the correct number of gate posts.