Fence Post Spacing & Quantity Guide: Panels, Gates and Concrete

Fence-post maths looks wonderfully simple until the fence acquires a corner, a gate, a panel size that does not match the drawing, or one last bay that is too short to be useful. The basic calculation is still simple, but the useful version is not just “length divided by spacing.” It is a small layout exercise.

This guide shows how to estimate posts for straight runs and closed perimeters, what gates do to the count, why pre-made panels need their own logic, and how to turn post holes into a concrete order. It uses both feet and metres so the same method makes sense whether your supplier talks about 8 ft panels, 1.83 m panels, pickets, palings, boards or mesh.

Think in Bays, Not Just Metres or Feet

A fence run is a chain of intervals. One interval may contain a panel, a set of pickets, a section of mesh or a gate. Posts sit at the boundaries between those intervals. That is why a straight run with five bays needs six posts: one at the beginning, four between the bays and one at the end.

Straight or open run
Fence bays = round up (net infill length ÷ maximum spacing)
Total intervals = fence bays + gate openings
Posts = total intervals + 1

Closed perimeter
Posts = total intervals

For pre-made panels
Fence bays = round up (net infill length ÷ actual panel or system module width)

Start with the Complete Fence Line

Measure the route the fence will actually follow, not the property area and not the straight-line distance between two points that the fence cannot use. Walk every side of the proposed run, mark corners, record changes in direction and note where gates must sit.

A small sketch prevents large ordering mistakes

Write a length beside every straight run instead of keeping one unexplained total in your head.

Mark every corner, free end, gate and change of fence type.

If two sides use different panels or different post spacing, calculate them as separate groups.

Keep the sketch until the order is placed; it becomes the easiest way to check where every post is supposed to go.

• Measure along the actual fence route.
• Separate disconnected fence runs.
• Mark corners before choosing the spacing.
• Record gate opening widths, not just gate-leaf widths from a catalogue.
• Check whether the supplier dimensions are panel width, clear opening, outside-to-outside width or post-centre spacing.
• Identify slopes, retaining edges and changes of ground level that may force a different layout.

Choose Post Spacing from the Fence System

There is no single correct spacing for every fence. A common DIY timber or picket layout in North America may place posts around 6–8 ft apart, while a pre-made panel system may dictate its own module. In Britain, many domestic fence panels are sold around 1.83 m wide, but the post itself can affect the repeated centre-to-centre dimension. Mesh, chain-link, metal and proprietary composite systems can use different spacing again.

Panel width and post spacing are not always the same number

This is one of the easiest mistakes to make when moving between suppliers or countries. A product described as an 8 ft panel may be intended for posts on 8 ft centres. Another system may sell a 1.83 m panel but require the post width to be included in the repeated run. The safe approach is to copy the dimension that the installation instructions actually use.

The supplier's module beats the label on the panel

Panel width describes the panel itself.

Clear opening describes the space between posts.

Centre-to-centre spacing includes part of each post and may be the dimension used by a panel system.

Do not mix these three measurements in one calculation.

Worked Example: 100 ft Straight Fence

The table uses maximum spacing. When the length does not divide evenly, reduce the spacing slightly across all bays instead of building twelve full bays and leaving an awkward short one at the end. The final set-out should still follow the selected fence system and any fixed gate or corner positions.

Worked Metric Example: 30 m Straight Fence

Gates Change the Layout Before They Change the Count

A gate removes ordinary fence infill from part of the run, but it does not remove structure. The opening still has boundaries, and those boundaries are posts. For quantity planning, subtract the combined gate width from the length filled with panels, pickets or mesh, then treat each gate opening as its own interval.

Place the gate on the sketch before distributing line posts

Mark the exact gate opening first.

Treat the gate as a structural interval, not as missing fence length.

Distribute ordinary fence bays on the remaining runs.

Verify whether the gate manufacturer requires larger posts, deeper foundations, bracing or different clearances.

Panels, Pickets and Mesh Need Different Quantity Logic

Post count is only one part of the order. The infill itself is purchased in different units. Pre-made panels are counted as complete sections. Pickets or palings are counted as individual pieces. Mesh is usually purchased by roll length. Mixing those methods is a reliable way to produce a very confident wrong answer.

A 1.83 m panel does not automatically create a 1.83 m centre spacing

For example, one UK panel manufacturer describes 1.83 m panels used with 100 mm slotted posts and shows a run calculation that adds a nominal 50 mm of post width per panel. The lesson is not that every British fence should use 1.88 m centres; the lesson is that the full installed module comes from the selected system.

An 8 ft panel may be designed for 8 ft post centres

In the US market, some 6 ft × 8 ft timber panels are explicitly intended to hang on 8 ft centres. Other products use different actual dimensions or installation details. Read the installation information for the exact panel rather than treating “8 ft” as a universal fence-post rule.

Concrete for Fence Posts Is a Volume Problem

Once the number of posts is known, concrete can be estimated from the hole geometry. The HomDera fence calculator uses the full cylindrical hole volume as a purchasing estimate, multiplies it by the number of posts, adds an editable allowance and divides the result by the mixed yield stated for one bag.

Gross volume of one round post hole = π × (hole diameter ÷ 2)² × hole depth

Total hole volume = volume per hole × number of posts

Order volume = total hole volume × (1 + concrete allowance ÷ 100)

Bags to buy = round up (order volume ÷ mixed yield per bag)

Diameter changes concrete volume faster than it looks

Round holes are cylinders, so volume depends on the square of the radius.

A modest increase in hole diameter can increase the concrete order noticeably.

Measure several holes when the auger wanders, the sides collapse or the soil changes.

Choose hole diameter and depth from the real fence design, not from a convenient calculator default.

This gross-hole method is deliberately simple and conservative because it does not subtract the volume displaced by the embedded post. A separate engineering or supplier method may calculate net concrete differently. The important point is to know which method your estimate uses and not mix assumptions halfway through the order.

Post-Hole Depth Is Not a Universal Fraction

You will often see simple rules such as burying roughly one-third of a post or using a familiar two-foot hole. Those can be useful reminders that posts need meaningful embedment, but they are not universal construction requirements. Frost depth, soil strength, drainage, fence height, wind, gate loads and the footing method can all change the required depth.

Corners and Separate Runs Need Their Own Set-Out

A total perimeter length is useful for budgeting, but it can hide awkward geometry. Imagine a 90 ft L-shaped fence made from a 50 ft run and a 40 ft run. Dividing 90 by 8 ft gives one answer for the total number of intervals, but each leg must actually finish at the corner post. Calculate the two legs separately so the corner lands where the corner exists in real life.

Common Fence-Post Estimating Mistakes

A Practical Fence Ordering Sequence

1. Confirm the boundary and proposed fence route.
2. Measure every straight run separately.
3. Mark corners, ends and gates on a sketch.
4. Choose the actual fence product or at least the intended construction type.
5. Copy the approved post spacing or panel module from the product information.
6. Calculate the bays between fixed points and round up where spacing is a maximum.
7. Add gate openings as structural intervals.
8. Count posts from the completed interval layout.
9. Calculate panels, pickets, rails or mesh using the correct purchasing unit.
10. Choose the post-hole diameter and depth required by the real design.
11. Calculate concrete from hole volume and exact bag yield.
12. Recheck the layout on site before buying or digging.

Frequently Asked Questions

How many fence posts do I need for 100 ft of fence?

For a straight run with no gates and a maximum spacing of 8 ft, 100 ft requires 13 bays and 14 posts. If the selected fence requires closer spacing, contains fixed corners or includes gates, the count changes.

How many fence posts do I need for 30 metres?

At a maximum spacing of 2.4 m, a 30 m straight run requires 13 bays and 14 posts. At a different approved spacing or when fixed gate and corner positions divide the run, calculate those sections separately.

Is 6 ft or 8 ft better for fence-post spacing?

Neither is universally better. Both appear in common timber-fence practice, but the correct maximum spacing depends on fence height, rails, post size, panel construction, wind exposure and the selected product. Use the spacing approved for the actual system.

Should posts be exactly 8 ft apart?

Only when the fence system specifically requires that module and the layout fits it. If 8 ft is a maximum spacing for a site-built fence, it is usually better to divide the run into a whole number of equal bays slightly below 8 ft than to leave one short final bay.

Do gates add two fence posts?

A gate opening normally has a post on each side, but it is safer to think of the gate as an interval in the layout than to blindly add two posts after the rest of the fence has already been counted. A gate at an end, paired gates or a shared post can otherwise be counted twice.

Do I need concrete for every fence post?

Not every fence system uses the same foundation method. Some posts are set in concrete, some use proprietary ground anchors, some metal systems use driven posts, and some installations use other approved details. Follow the selected fence and site requirements rather than assuming one method for every post.

How many bags of concrete does one fence post need?

There is no universal bag count. Calculate the hole volume from diameter and depth, decide whether your method uses gross or net concrete volume, add any justified allowance and divide by the mixed yield printed on the selected bag. Bag weight alone is not enough.

Can I calculate a closed backyard perimeter as one number?

For a simple rectangular loop with no fixed complications, a total perimeter can provide an early count. For the final set-out, calculate each side between corners so every corner post lands at the real corner and each side receives sensible spacing.

Useful Product and Installation References

These references are useful examples of why fence dimensions must be taken from the selected system. They are not universal construction standards and do not replace local requirements.

Final Fence Check

• Every straight run has been measured separately.
• Corners, free ends and gates are marked on the layout.
• The spacing comes from the actual fence system or an appropriate design.
• Pre-made panels use the correct installed module rather than a guessed nominal width.
• Gate posts and gate foundations have been checked separately where required.
• The post count follows the real number of intervals.
• Concrete uses the chosen hole dimensions and exact bag yield.
• Boundary, underground services, drainage, soil and local requirements are checked before digging.
• The final material quantities are rounded to the units the supplier actually sells.

The most reliable fence estimate is not the one with the cleverest formula. It is the one that matches the real line on the ground. Measure the route, place the fixed features, divide the remaining runs into workable bays, then count the posts, infill and concrete. Once every interval has a job, the order becomes easier to explain—and much less likely to end with one lonely post, two missing panels and an emergency trip to the supplier.