Outdoor
Post Hole Calculator
Calculate concrete needed for fence post holes, deck posts, and mailbox posts. This calculator accounts for the hole diameter, depth, and post size to give accurate concrete requirements.
Enter Your Measurements
Formula Used
Concrete Volume = (Hole Volume) - (Post Volume in ground)
Pro Tips
- •Hole should be 3x the width of the post
- •In cold climates, holes must go below frost line
- •Slope concrete away from post for water drainage
- •Allow 24-48 hours before attaching rails or loads
Frequently Asked Questions
How deep should fence post holes be?
Fence post holes should be 1/3 to 1/2 the height of the fence. A 6-foot fence needs posts at least 2-3 feet deep.
How wide should a post hole be?
The hole should be about 3 times the width of the post. For a 4x4 post, use a 12-inch diameter hole.