How Many Bags of Concrete for a Fence Post?
Updated
Most fence posts need 1 to 4 bags of concrete each, depending on hole size. A standard 4-inch post in a 10-inch-wide, 2-foot-deep hole takes about 2 bags of 50-lb fast-setting concrete. Bigger posts and deeper holes need more — use the table below to plan.
Setting fence posts in concrete is the difference between a fence that lasts decades and one that leans after a season. The amount of concrete per post depends on the hole's diameter and depth — and it's easy to underestimate.
This guide gives the bags-per-post by hole size, the right depth for a sturdy post, and a quick reference so you buy the right amount the first time.
Key takeaways
- Most posts need 1–4 bags of concrete each.
- A standard post (10-in hole, 2 ft deep) takes about 2 bags.
- Hole depth should be 1/3 to 1/2 the above-ground post height.
- Hole width should be about 3x the post width.
- Fast-setting concrete can be poured dry and set with water.
Skip the math
Get instant numbers with the Concrete Calculator.
Bags per post by hole size
This assumes a 4-inch post and 50-lb bags of fast-setting concrete (each yields about 0.375 ft³).
| Hole diameter | Hole depth | 50-lb bags per post |
|---|---|---|
| 8 in | 2 ft | 1 – 2 |
| 10 in | 2 ft | 2 |
| 10 in | 3 ft | 3 |
| 12 in | 3 ft | 4 |
How deep should a fence post hole be?
A good rule is to bury 1/3 to 1/2 of the post's above-ground height. For a 6-foot fence, set posts about 2 to 3 feet deep — and always below your local frost line to prevent heaving.
How wide should the hole be?
Make the hole about three times the width of the post — roughly 9–12 inches for a standard 4×4 post. This gives the concrete enough mass to hold the post firmly.
Estimating concrete for all your posts
Multiply the bags-per-post by your number of posts, then add a couple of spares. Our concrete calculator can also work out the total volume if you'd rather buy in bulk for a long fence line.