What Size Auger Do I Need?
Choosing the best auger size for your project depends on the project itself. Auger size, and thus hole size, is an important element of the project, as drilling holes of the wrong size will delay the rest of the project. Two common projects are post hole digging and gardening. While these are not the only applications for auger use, the factors that determine auger size for these projects may help guide you for other projects.
As always, remember to search and follow local codes and regulations. You can call 811 before digging to check for utility lines and more information.
Post Holes
For post hole digging, you must consider the support of your post. The most common support is a cement base, whose size depends on the post and whether it has a steel plate base or not.
A general rule for post hole digging is to have 1 inch of cement around the post to repack the dirt. Additionally, it is better to dig wider than needed for post hole digging in case you need to realign.
Our recommendations for post hole digging are as follows:
- For a 1 7/8" Steel Post, use a 6" auger.
- For a 2 3/8" Steel Post, use a 6" auger.
- For a 4" x 4" Wood Post for mailboxes, use an 8" auger.
- For a 4" x 4" Wood Post for fencing, use an 8" auger.
- For a 6" x 6" Wood Post, use a 12" or larger auger.
Gardening
Gardening and digging for larger plants can be done more efficiently using an auger, but the size of the auger will depend on the plant, the soil conditions, and the geological location. For seeds, bulbs, and small potted plants, augers of 2" to 4" in diameter can be used. Larger plants with a base measured in gallons or pot width generally correspond to the following auger sizes:
- For a 1-quart pot, you will need a 6" auger.
- For a 2-quart pot, you will need an 8" auger.
- For a 3-quart pot, you will need a 10" auger.
- For a 5-quart pot, you will need a 12" auger.
Other Applications
For jobs like soil sampling, anchoring, and seeding, smaller augers with 2" to 4" diameters are used. Smaller augers put less stress on the operator and require less force and effort to refill the hole after installation.
To shop augers, choose one of the following types of augers and subsequently select the size you need.
*If your soil is hard-packed or digging deeper than 2 feet, you can size up your auger, and you may consider replacing your blades and points accordingly. A guide for auger points and blades in the appropriate soil type is provided in this article: Auger Comparison, Use, And Attachment Information.