Prices last reviewed: October 2026
How many fence posts do I need?
Split each side into sections no wider than your post spacing. You need one post per section, one more to finish an open fence and one extra for each gate. Sides that meet at a corner share the corner post.
posts = sections + 1 + gates
sections = length of each side / post spacing, rounded up
| Straight fence, posts every 8 ft | Posts | Bags of concrete (50 lb) |
|---|---|---|
| 50 ft | 8 | 20 |
| 100 ft | 14 | 35 |
| 150 ft | 20 | 50 |
| 200 ft | 26 | 64 |
| 300 ft | 39 | 96 |
Concrete figures are for 4x4 posts in 10 in holes set 2 ft deep, as for a 6 ft wood fence.
How far apart should fence posts be?
| Fence type | Typical post spacing |
|---|---|
| Wood privacy, board-on-board, picket | 8 ft or less |
| Wood or vinyl panels | The panel width, usually 6 or 8 ft |
| Chain link | Up to 10 ft |
| Split rail | About the rail length, usually 10 ft |
Closer spacing makes a stronger fence. In windy areas or for tall privacy fences, 6 ft spacing is worth considering.
How deep should fence posts be?
A common rule is to bury one third of the fence height, and never less than 2 ft. The post length is the fence height plus the buried depth, rounded up to the next standard post length.
| Fence height | Depth in ground | Wood post to buy |
|---|---|---|
| 3 ft | 2 ft | 6 ft |
| 4 ft | 2 ft | 6 ft |
| 5 ft | 2 ft | 8 ft |
| 6 ft | 2 ft | 8 ft |
| 8 ft | 3 ft | 12 ft |
In cold climates, set posts below the frost line so frost cannot push them up. Your local building department can tell you the frost depth.
How much concrete per fence post?
Concrete fills a round hole to the buried depth, minus the space the post takes up. One 50 lb bag of fast-setting concrete makes about 0.375 cubic feet.
bags per post = (hole volume − post volume) / 0.375
| Post | Hole | Depth | 50 lb bags per post |
|---|---|---|---|
| 4x4 wood | 8 in | 2 ft | 1.4 |
| 4x4 wood | 10 in | 2 ft | 2.5 |
| 4x4 wood | 12 in | 2 ft | 3.7 |
| 4x4 wood | 10 in | 3 ft | 3.7 |
| 6x6 wood | 12 in | 2 ft | 3.1 |
| 6x6 wood | 12 in | 3 ft | 4.6 |
| 5x5 vinyl | 10 in | 2 ft | 2.0 |
| Chain link line post, 1-5/8 in | 8 in | 2 ft | 1.8 |
| Chain link terminal post, 2-3/8 in | 8 in | 2 ft | 1.7 |
If you buy 80 lb bags instead, each makes about 0.6 cubic feet, so you need about 0.63 times as many bags. The calculator rounds the total for the whole fence up to whole bags, so you do not buy a partial bag for every post.
Tips for setting fence posts
- Hole size: a common rule is three times the post width. That is about 10 in for a 4x4 post.
- Gravel base: put a few inches of gravel in the bottom of each hole for drainage. The calculator adds one 0.5 cu ft bag per hole.
- Crown the top: slope the concrete away from the post at ground level so water runs off.
- Gate posts: use a larger hole or a 6x6 post, because gates pull hard on their posts.
- Call 811 before you dig, so buried lines are marked for free.
More fence calculators
- Fence cost calculator for the full materials list and total cost
- Wood fence calculator
- Chain link fence calculator
Frequently asked questions
How many bags of concrete do I need per fence post?
About 2.5 bags of 50 lb fast-setting concrete for a 4x4 post in a 10 in hole set 2 ft deep. A deeper or wider hole takes more: about 3.7 bags for a 10 in hole 3 ft deep, or for a 12 in hole 2 ft deep.
How many fence posts do I need for 100 ft?
With posts every 8 ft, a straight 100 ft fence needs 14 posts. With chain link posts every 10 ft, it needs 11. Each gate adds one more post.
How deep should a fence post be?
One third of the fence height, and at least 2 ft. For a 6 ft fence that is 2 ft, so you buy 8 ft posts. For an 8 ft fence it is about 3 ft, so you buy 12 ft posts.
How far apart should fence posts be?
8 ft or less for wood fences, the panel width for panel fences, up to 10 ft for chain link and about the rail length for split rail.
Should I use 4x4 or 6x6 fence posts?
4x4 posts are standard for fences up to 6 ft. 6x6 posts are a good choice for gates, 8 ft fences and windy sites because they resist bending.
Fast-setting or regular concrete for fence posts?
Fast-setting concrete is poured dry into the hole and then soaked with water, so there is no mixing. It sets in under an hour, which makes it the most popular choice for fence posts. Regular concrete is cheaper per bag but needs mixing and longer to cure.