Fence calculator
Panels, posts and the real spacing between them.
Your inputs
Your inputs are processed on your device and are not sent to a server.
Example loaded. You can change any value.
There is no figure yet: nothing is calculated until you ask for it.
- Enter your measurements.
- Check the units and the assumptions.
- Press Calculate, or load the example.
Rather see a worked case? Press “Load example” and change any value afterwards.
Next step
Each post is set in concrete, and you already know how many there are.
Where each number comes from Conversion constants are exact; densities and coverage rates come from cited sources; everything else is an assumption you can change. Methodology · Sources and updates
How to use it
- Measure the total run of the fence.
- Enter the width of the panels you will use.
- Subtract the width of any gates.
- Say whether the run is straight or a closed perimeter.
How it is calculated
Two simple sums and one rule that changes the post count:
A straight run always needs one more post than panels: one at each end of every panel, sharing the intermediate ones. In a closed perimeter the last panel meets the first post, so posts equal panels.
The result includes the real spacing between posts, which rarely matches the nominal panel width: the last bay is adjusted by cutting.
Worked example
A 66 ft fence with 8 ft panels, straight run, no gates:
- Panels: 66 / 8 = 8.25 → 9 panels
- Posts: 9 + 1 = 10 posts
- Real spacing: 66 / 9 = 7.3 ft
The last panel has to be cut down. That is normal; the only decision is whether the cut goes at the end or is shared across bays, which looks better.
Good to know
- Posts get concreted in. Allow 30-40 litres (about 1.2 cubic feet) of concrete per post for a medium-height fence.
- Sloping ground. Panels are either stepped or raked; either way you need a little more material.
- Gates. Their posts take more load and are usually heavier and set deeper.
- Measure the ground, not the plan. Boundaries are rarely perfectly straight.
Frequently asked questions
How many fence posts do I need?
On a straight run, one more than panels: 9 panels need 10 posts. On a closed perimeter, posts equal panels, because the last panel closes against the first post.
How many fence panels do I need?
Divide the run by the panel width and round up. For 66 ft with 8 ft panels that is 9 panels, with the last one cut to fit.
How far apart should fence posts be?
Whatever the panel dictates, usually 6 to 8 ft. Wider spacing needs heavier posts and stiffer panels.
How much concrete does each post need?
It depends on fence height and ground conditions, but 1 to 1.4 cubic feet per post is a reasonable starting point. The concrete calculator gives the exact volume per hole.