Concrete for Fence Post Holes

This page opens the concrete calculator set up for fence posts, deck posts or mailbox posts — any job with several identical round holes to fill. Enter the diameter of one hole (in inches or centimeters — post-hole augers are sized that way), the depth (in feet or meters), and how many holes you're filling; the calculator computes one hole's volume with π × radius² × depth and multiplies by the count.

A common fence post hole is 8–12 inches across and 24–36 inches deep, depending on frost line and local code — always check your area's minimum footing depth before digging, since post stability depends on getting below the frost line, not just on the concrete volume. A 10-inch-diameter, 2-foot-deep hole holds about 1.09 ft³; six of those holes total about 6.5 ft³, roughly 15 bags of 60 lb pre-mix.

Post holes are usually filled with dry-set or quick-set concrete rather than a wet pour, and the waste checkbox's 10% margin is worth keeping ticked here — irregular auger holes rarely come out as a perfect cylinder, and a partly filled hole around a post is not a job worth repeating. Everything is calculated locally in your browser.