How deep to go
| Use | Published figure | Source |
|---|---|---|
| Gravel at the bottom of the hole | 6 in | quikrete.com |
| Hole depth | 1/3 to 1/2 of post height above ground | quikrete.com |
Quikrete's post-setting instructions say to pour 6 inches of gravel or crushed stone into the bottom of the hole and compact it with the post or a 2 × 4. Its video adds that the hole should be 1/3 to 1/2 as deep as the post is tall above ground, so a 6 ft fence needs holes at least 2 ft deep, plus the 6 inches for gravel.
Working it out
Cubic feet per hole = 3.1416 × (diameter ÷ 2)² × gravel depth ÷ 1,728 (all in inches).
Example: 10 holes 10 inches across with 6 inches of gravel take 0.273 cubic feet each, 2.73 cubic feet in all, or 6 bags of 0.5 cu ft.
Rochester Concrete Products' install guide adds 10% for compaction and uneven ground.
Common questions
How much gravel do I need for a fence post gravel?
Measure the area, choose a depth from the table above and enter both in the calculator. It gives cubic yards, tons and bags.
Should I order extra?
Rochester Concrete Products' install guide adds 10% for compaction and uneven ground. Loose stone also compacts, so a compacted layer needs more loose material than its finished depth suggests.
Related calculators
Sources
- https://www.quikrete.com/athome/SettingPostsInstructions.asp
- https://www.quikrete.com/AtHome/Video-Setting-Posts.asp
- https://www.doitbest.com/product/276837/