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Concrete Calculator
Material Calculators

Concrete Calculator

Calculate cubic yards, bags needed, and cost for any concrete project.

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How to calculate concrete for a slab or footing

  1. Measure your project — length, width, and thickness. For a 10×12 patio at 4 inches deep, those three numbers are all you need.

  2. Enter the dimensions and select your shape. Switch from "slab" to "column" if you're sizing round piers; enter diameter and height instead.

  3. Enable the 10% waste buffer. Poured concrete always spreads a bit, forms flex under pressure, and some sticks to tools.

  4. Check the cubic yards for a ready-mix order, or read the bag count. Anything under about 1 yard, bags are usually the practical choice.

Common uses

  • Sizing a patio, garden path, or garage floor slab
  • Calculating bags for fence post or mailbox footings
  • Estimating footing volume for a deck, shed, or retaining wall

Frequently asked questions

How much concrete do I need for a 10×10 slab at 4 inches thick?
A 10×10 slab at 4 inches deep is roughly 1.23 cubic yards — that's about 56 bags of 60 lb concrete or 42 bags of 80 lb, before the waste buffer.
Bags or ready-mix — which should I use?
Bags are easier for small pours under about 1 cubic yard. For bigger jobs, a ready-mix truck costs less per yard and saves a lot of manual mixing.
How thick should a residential driveway be?
Four inches is standard for everyday cars. If you park trucks, vans, or heavy equipment on it regularly, bump that up to 5–6 inches and add wire mesh.
What happens if I order too little concrete?
Running short mid-pour is a serious problem — you can't patch fresh concrete cleanly. Always add at least 10% to your estimate. Leftover concrete can go into any small project.

Not sure whether to DIY this project?

Read our project-by-project guide on when to hire a contractor vs. do it yourself.

Read the guide →

About this calculator

Enter your slab, column, or stair dimensions to instantly calculate cubic yards, 60lb and 80lb bag counts, and estimated cost. Includes a 10% waste buffer option. 100% client-side.

All results are estimates. Verify quantities with your local supplier and confirm measurements before purchasing materials. Requirements vary by region and project type.

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