Measuring a Fence Layout Around Corners and Gates

Start with a topology, not one perimeter number

Walk the proposed fence line and make a simple plan. Give each end, corner, change of direction, and each side of a gate its own physical post location. Then record every uninterrupted fence run between those locations. A corner shared by two runs is one post, not two. A gate is an interruption: it normally has its own endpoint posts and hardware, but it is not a fence bay or panel.

This guide gathers inputs; it does not select a fence system, post size, gate clearance, spacing, footing depth, frost protection, concrete mix, or structural design. Use the selected system's current instructions, project documents, authority requirements, and qualified advice where applicable.

Record clear bay width and centre spacing separately

A clear bay is the open distance between post faces. Centre-to-centre spacing includes the post face dimension: for equal posts on a straight run, centre spacing = clear bay width + one post-face width. Do not silently substitute one for the other when measuring or ordering panels.

For example, Barrette Outdoor Living's pre-built aluminum fence instructions describe a system-specific post-location measurement as panel width plus post width, and tell installers to plan gate placement and hardware clearance before installation. That is a useful check for that system, not a universal bay, gate, or hole rule. Read the instructions matching the exact product you selected.

Worked layout: an L-shaped 10 m + 4 m fence

Suppose the selected system or project constraints allow a maximum clear bay width of 2 m. There is no gate in this counting example.

1. First uninterrupted run: 10 m ÷ 2 m = 5, so it needs 5 bays and 6 posts along that straight run.
2. Second uninterrupted run: 4 m ÷ 2 m = 2, so it needs 2 bays. Its corner endpoint is already one of the first run's six posts, so this run adds only 2 new posts.
3. Totals: 5 + 2 = 7 fence bays; 6 + 2 = 8 unique posts.

The result is not 9 posts: adding “6 posts” and “3 posts” would count the shared corner twice. If a 2 m gate opening interrupts a run, measure it as its own gate edge with two endpoint posts, record its actual opening and hardware clearance, and do not count it as a fence bay. Recalculate each remaining fence segment independently; do not subtract a gate width from a perimeter and divide the remainder blindly.

Measure post-hole concrete as a separate geometry task

After the layout has established the hole count, measure the dimensions actually specified for each hole group: shape and inside dimensions, concrete-filled height, post section, and how much of the post overlaps the concrete. If gravel or filler occupies part of the hole, keep that outside the concrete-filled height. Different terminal, corner, gate, or soil-condition details may have different measured geometry, so calculate them as separate groups.

Illustrative eight-hole concrete example

Using the eight unique posts above, assume each group has a measured 0.30 m diameter round hole, 0.60 m concrete-filled height, and a 0.09 m × 0.09 m square post through that same 0.60 m height. These are example inputs only—not a depth or diameter recommendation.

1. Hole volume per post: π × (0.30 m ÷ 2)² × 0.60 m = 0.042412 m³.
2. Post displacement per post: 0.09 m × 0.09 m × 0.60 m = 0.004860 m³.
3. Concrete per post: 0.042412 m³ − 0.004860 m³ = 0.037552 m³.
4. Net concrete for eight holes: 8 × 0.037552 m³ = 0.300416 m³, or 300.416 L.
5. Example bag check: at a stated yield of 10.6 L/bag, 300.416 L ÷ 10.6 L/bag = 28.341 bags, so round up to 29 whole bags before any separately chosen ordering allowance.

Enter the exact product yield printed for the bag you will buy. The 10.6 L value is the product-specific example used by the Post-Hole Concrete Calculator, not a universal bag yield.

Use the measurements in the right estimator

• Fence Materials Calculator (C03): enter each fence run and gate as separate edges; it counts shared topology posts once and reports bays, materials, and post holes.
• Post-Hole Concrete Calculator (C04): use the counted holes and each measured hole/post geometry to estimate concrete volume and bags.
• Fence Installation Cost Calculator (C14): combine this measured topology and post-hole quantities with editable supplier quotes, separately priced gates, and labor.
• Fence & Deck Stain Calculator: after selecting the fence finish and measuring the paintable surface, estimate coating quantity separately from layout and concrete.