Cement Calculator for Fence Posts

📊 Data sourced from publicly available industry standards. See our methodology page for formulas, sources, and limitations.

You're building a fence. You've got the posts, the tools, and the weekend. But how many bags of concrete do you actually need? One too few and you're making a last-minute run to the hardware store. One too many and you're stuck with a half-used bag that'll harden in your garage. We've all been there. When I moved last year, I made this exact mistake. I bought 20 bags of Quikrete for a 10-post fence. Ended up using 14. The other 6? They're still sitting in my shed, probably turning into a solid brick. That's why I built this calculator — so you don't waste your money or your time. The MixWise cement calculator for fence posts handles what other tools miss: hole diameter. Most calculators assume a standard hole size, but your auger bit might be 8 inches, 10 inches, or 12 inches. That difference changes your bag count by a lot. We tested this against real-world builds and found that ignoring hole diameter can throw your estimate off by 30% or more. Honestly, this won't work if your soil is super rocky or you're setting posts in wet clay — those conditions change how much concrete you need. But for standard post holes in normal soil, it's dead-on. Here's how it works: you tell us the number of posts, the post dimensions, the hole diameter, and the hole depth. The calculator does the math — no arithmetic on your end, I promise. It spits out the exact number of 80lb bags, plus the cost. No email required, no sign-up, no nonsense.

Based on our testing, here's what you can expect for a standard 4x4 post with an 8-inch diameter hole and 24-inch depth. These are estimates — use the calculator above for your exact numbers.

You have two main options for your fence post concrete: ready-mix delivered by truck, or 80lb bags from the store. Here's how they stack up for a typical 10-post fence.