4x4-inch posts will typically fit into holes drilled by a 6-inch diameter auger bit. However, this leaves little to no room for cement or dirt to pack in and secure the post. For this reason, we recommend using an 8- to 10-inch diameter auger to leave room for packing in the materials needed to secure the post.

A one-man auger can typically dig around 3 feet deep, which is satisfactory for most fence posts, planters or other lawn applications. If you need to dig even deeper, a two-man auger can typically dig up to 5 feet. That depth is ideal for applications in cold climates where frost can penetrate more than 3 feet. Read our Project Uptime article, How to Use a Gas Powered Auger (The Right Way).

The auger diameter is measured by adding the shaft diameter to two times the strip width. United Rentals provides auger rentals with diameters between 2 and 18 inches.

The most suitable post hole auger diameter depends on the application. Earth augers with 2- to 3-inch diameters are best for gardeners who plant bulbs, install small stakes and poles and perform root aeration. Auger rentals with 4-to 5-inch diameters work for smaller fence posts and plants that come in quart-sized pots. Choose a 7-inch diameter for plants in gallon-sized pots and drilling holes for 4x4 fence posts. Finally, augers with 8- to 9-inch diameters work for plants in two-gallon pots and drilling holes for larger 6x6 fence posts.

Typical post hole augers dig around 3 feet deep, but you may need to dig even deeper depending on the height of the fence posts. Contact your local United Rentals branch for more information.