Fence post & panel calculator
Enter each side of the fence and its gates. You get every post by type, the panels or rails and pickets, post length, and the concrete and gravel for the holes.
Fence materials
100 ft of fence in 2 sides, 1 gate, panels fixed to the post faces, 6 ft high, posts 3 ft in the ground.
- Posts15 × 10 ftcut to 9 ft each
- Panels132 cut to fit
- Concrete56 × 50 lb3.7 bags per post
Fence length 96 ft plus 1 gate · 13 bays of up to 8 ft centre to centre
| Item | Count | Notes |
|---|---|---|
| Line posts | 10 | between the bays |
| Corner posts | 1 | shared by two sides |
| End posts | 2 | where the fence stops |
| Gate posts | 2 | 2 per gate; heavier posts help |
| All posts | 15 | 9 ft long: 6 ft above + 3 ft below ground |
| Panels | 13 | 8 ft wide, 2 cut down |
| Gates | 1 | 4 ft openings, with hinges and a latch each |
| Concrete | 56 × 50 lb | 0.76 yd³ (20.7 ft³) in 10 1/2 in holes |
| Gravel under posts | 4.51 ft³ | 6 in per hole, about 473 lb |
Gates are assumed evenly spread along their side. Moving one changes the count by a post at most.
How to use the fence calculator
Measure each straight side of the fence and enter it as a side; each new side starts at a corner, and the corner post is shared. Put the number of gates on each side and the gate opening. If the fence goes all the way round and meets itself, tick the box so the last corner is not counted as two ends.
Pick the style. Panels on the post faces put the posts one panel width apart. Panels between posts add the post width to that. Rails and pickets use your maximum post spacing, and the pickets are counted from their width and gap.
Posts and concrete
QUIKRETE's post-setting guide gives two rules of thumb, used here as starting values: a hole three times the post's width, and a third of the post's total length in the ground, which is half the height above it. Six inches (150 mm) of gravel goes under the post for drainage, and the concrete stops 3 to 4 in (75 to 100 mm) below ground so soil can cover it. Bags are counted from the mixed volume printed on the bag.
Worked example
A 60 ft side with one 4 ft gate and a 40 ft side, in 8 ft panels: the gate leaves 56 ft of fence on the first side in two runs of 28 ft, each 4 bays. The second side is 5 bays. That is 13 panels, 2 of them cut, and 10 line posts plus 1 corner, 2 end and 2 gate posts: 15 posts of 9 ft.
How deep should fence posts go?
The third-of-the-length rule sets a 6 ft fence post 3 ft down, on a 9 ft post. Many fences are built shallower, and some places need deeper: where the ground freezes, posts set above the frost line can heave. Your local building department can tell you the frost depth and whether a fence of your height needs a permit, and some areas limit fence heights near roads and boundaries. Call your local utility locating service before digging (811 in the US).
Sources
- QUIKRETE, Setting Posts project guide: hole three times the post diameter, depth one third of the post length plus 6 in of gravel, concrete to 3–4 in below the top.
- QUIKRETE, Concrete Mix (No. 1101) data sheet: yields of 0.30, 0.375, 0.45, 0.60 and 0.675 ft³ for 40, 50, 60, 80 and 90 lb bags.
- Easy Mix, Concrete Supremo 32MPa data sheet: about 10 L (0.01 m³) per 20 kg bag. Our 25 and 30 kg yields are scaled from these two labels.
Questions
How many posts do I need for a 100 ft fence?
In one straight line with posts 8 ft apart, 100 ft is 13 bays (the last one shorter), so 14 posts. Each corner, gate or extra side changes the count, which is why the calculator works side by side.
How many bags of concrete per fence post?
It depends on the hole. A 10 1/2 in hole with a 4 × 4 post, filled to 32 in deep, holds about 1.4 ft³ of concrete: a little over two 80 lb bags at 0.60 ft³ each, or nearly four 50 lb bags. Smaller, shallower holes take much less; the calculator shows bags per post for your sizes.
Do gate posts need to be bigger?
A gate hangs its whole weight off one post and swings, so many builders use a heavier post, a deeper or wider hole, or both, for gates. The calculator counts two gate posts per gate; change the post width or hole size if yours will be different.
What if a side is not a whole number of panels?
The last bay of each run is shorter, so one panel is cut to fit. The calculator counts it as a full panel and tells you how many need cutting. You can also spread the difference by setting posts slightly closer.