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Landscaping & Outdoor

Fence Calculator

Posts, sections, rails and concrete for a run of fence, with gate openings taken out of the run.

Your measurements

Gate openings are deducted before the sections are worked out.

The run
Measured centre to centre. Six feet resists sag and wind far better on a solid privacy fence.
Gates and rails

Your result

Sample values

14

Posts

12

Sections

38

Rails

28

Bags of concrete

100 ft run less one 4 ft gate, 8 ft spacing, 3 rails, 5% waste.

What to order

Item Quantity
Posts 14
Rails 38
Concrete, 60 lb bags 28 bags
Gate hardware sets 1 set

How to use this calculator

Enter the whole length of the fence line and how many gates you are hanging. Gate openings come out of the run first, because a gate is not a fence section and does not need rails or pickets.

Post spacing is centre to centre. Eight feet is the usual maximum and matches standard rail lengths; drop to six on exposed sites or where the panels are solid, since a privacy fence catches wind like a sail.

Formula

Fenced run = Length − (Gates × Gate width)

Sections = ceil(Fenced run ÷ Spacing)

Posts = Sections + 1 + Gates

Rails = Sections × Rails per section × (1 + Waste)

+ 1
the post at the far end — ten bays need eleven posts
+ Gates
each gate needs its own hanging post

Concrete is estimated at 2 bags of 60 lb mix per post.

Worked example

A 100 ft fence with one 4 ft gate, 8 ft spacing, 3 rails per section, 5% waste.

  1. Fenced run: 100 − (1 × 4) = 96 ft
  2. Sections: ceil(96 ÷ 8) = 12
  3. Posts: 12 + 1 + 1 gate post = 14
  4. Rails: 12 × 3 = 36, × 1.05 = 38
  5. Concrete: 14 posts × 2 bags = 28 bags

14 posts, 12 sections, 38 rails

Understanding your results

The post count is the number people get wrong, and always in the same direction. A run of twelve sections needs thirteen posts, plus one more for each gate, because posts sit at both ends of every bay. Ordering twelve leaves you one short on the last afternoon.

Rails carry a waste allowance and posts do not. Rails get cut to fit the last bay and around gates; posts are used whole or not at all, so there is nothing to waste.

Questions

About this calculator

Ask something else

Eight feet centre to centre is the usual maximum and suits standard rail lengths. Six feet is better for solid privacy panels, on windy sites, or where the ground is soft, because it cuts the load on each post by a quarter.

Almost never. The calculator rounds sections up, so the final bay is short and gets a cut rail. Setting out from the most visible end keeps the odd bay where it is least noticeable, usually at a corner or against the house.

Yes for anything but a light pedestrian gate. A gate hangs its whole weight off one post and swings it repeatedly, so a 6 × 6 in gate post set deeper than the line posts is normal practice. That upgrade is not in the count here.

The estimate here is two 60 lb bags per post, which suits a 4 × 4 in post in a 10 in hole around two feet deep. Deeper holes for taller fences or frost need more — the post depth calculator works out the volume properly.

Keep going

All Landscaping & Outdoor tools
Estimates, not specifications. Results are based on the values you enter and on typical material properties. Densities, coverage rates and product sizes vary between suppliers, so confirm quantities against your supplier's data before ordering. Structural work must be signed off by a qualified professional and meet your local building code.