Fence Post Chart: Posts, Rails and Concrete by Fence Length
Twelve fence lengths at three post spacings, then the whole material list at eight foot spacing, then the concrete a hole takes at every normal depth and diameter.
Posts are sections plus one. That plus one is where the count goes wrong, and it goes wrong again at every corner and every gate, because each of those needs a post of its own that the straight line arithmetic never sees.
The concrete is the part people underestimate. A 10 inch hole 30 inches deep takes just over a cubic foot once the post is subtracted, which is four 50 pound bags for one post, and a 150 foot fence is eighty bags on a pallet.
Posts by fence length and post spacing
| Fence length | 6 ft spacing | 8 ft spacing | 10 ft spacing |
|---|---|---|---|
| 50 ft | 10 | 8 | 6 |
| 75 ft | 14 | 11 | 9 |
| 100 ft | 18 | 14 | 11 |
| 125 ft | 22 | 17 | 14 |
| 150 ft | 26 | 20 | 16 |
| 175 ft | 31 | 23 | 19 |
| 200 ft | 35 | 26 | 21 |
| 250 ft | 43 | 33 | 26 |
| 300 ft | 51 | 39 | 31 |
| 400 ft | 68 | 51 | 41 |
| 500 ft | 85 | 64 | 51 |
| 660 ft | 111 | 84 | 67 |
The whole material list at 8 ft spacing
| Fence length | Sections | Posts | Rails | Pickets | 50 lb bags |
|---|---|---|---|---|---|
| 50 ft | 7 | 8 | 21 | 110 | 32 |
| 75 ft | 10 | 11 | 30 | 164 | 44 |
| 100 ft | 13 | 14 | 39 | 219 | 56 |
| 125 ft | 16 | 17 | 48 | 273 | 68 |
| 150 ft | 19 | 20 | 57 | 328 | 80 |
| 175 ft | 22 | 23 | 66 | 382 | 92 |
| 200 ft | 25 | 26 | 75 | 437 | 104 |
| 250 ft | 32 | 33 | 96 | 546 | 132 |
| 300 ft | 38 | 39 | 114 | 655 | 156 |
| 400 ft | 50 | 51 | 150 | 873 | 204 |
| 500 ft | 63 | 64 | 189 | 1,091 | 256 |
| 660 ft | 83 | 84 | 249 | 1,440 | 336 |
Concrete per hole, by depth and diameter
| Hole depth | 8 in hole | 10 in hole | 12 in hole |
|---|---|---|---|
| 24 in | 0.53 | 0.92 | 1.4 |
| 30 in | 0.66 | 1.15 | 1.75 |
| 36 in | 0.79 | 1.38 | 2.1 |
| 42 in | 0.92 | 1.61 | 2.45 |
| 48 in | 1.06 | 1.84 | 2.8 |
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The fence calculator takes your own measurements and returns the number for your job, plus the material list as a printable document. Every cell in the table above came out of that same calculator, run at build time.
Depth is set by the frost line, not by the fence
The rule of thumb is a third of the post in the ground, so a 6 foot fence on an 8 foot post gets 24 to 30 inches. That rule loses to the frost line wherever the frost line is deeper, because a post set above it will be lifted out of the ground over a few winters whatever the concrete does.
Northern states run 36 to 48 inches. Much of the south has no frost requirement at all and the depth is about wind and soil instead. Check the local code, and check it for gate posts separately, since many jurisdictions want those deeper.
Spacing is a trade between posts and rails
Eight feet is the default because rails and panels are sold in eight foot lengths, so a shorter spacing wastes rail and a longer one needs a splice. Six feet is what you go to for a tall privacy fence in wind, or for anything on a slope where the panels have to step.
Ten feet appears on ranch rail and wire fence where the rail is long and the load is light. It is not a good idea in a solid privacy fence, where every section is a sail.
Corners, ends and gates need their own posts
The count in the first table is a straight run. Every corner is a post that carries two directions of pull, every end is a post, and a gate needs a post on each side, usually heavier than the line posts and set deeper.
A gate post that moves is the single most common fence failure, and it is almost always a depth problem rather than a concrete problem. A 4 x 4 carrying a wide gate will eventually lean, which is why gates over about four feet wide get a 6 x 6.
Picket count is a division, and the gap is the variable
Pickets butted tight at 5.5 inches gives about 2.18 pickets a foot. A quarter inch gap drops that to about 2.09, and a shadow box or a spaced picket fence drops it further, which is the whole reason the calculator takes the gap as a separate input.
Order a few percent over. A pressure treated picket pack always contains two or three that are twisted enough that nobody wants them on the street side.
Questions people ask
How many posts do I need for a 100 foot fence?
Eleven at 10 foot spacing, fourteen at 8 foot spacing, and eighteen at 6 foot spacing, before adding a post for each corner and each side of every gate.
How many bags of concrete per fence post?
About four 50 pound bags for a 10 inch hole 30 inches deep, or three 60 pound bags. A 12 inch hole 36 inches deep takes about six 50 pound bags.
How deep should a fence post be?
A third of the post length is the usual starting point, so 24 to 30 inches for a 6 foot fence, but the frost line overrides it. In cold states that means 36 to 48 inches.
How far apart should fence posts be?
Eight feet is standard because rails and panels come in eight foot lengths. Six feet is better for tall privacy fence, exposed sites and slopes.
Do I need concrete for every post?
Line posts in well drained soil are sometimes set in compacted gravel, which drains and can be reset. Corner, end and gate posts carry real load and almost always get concrete.