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Concrete Calculator
Concrete Calculator
Material Calculators

Concrete Calculator

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

DIY difficulty

ModerateTypical time: Half a day to full day
  • ›Mixing and pouring is physically demanding
  • ›Timing matters — concrete sets fast on hot days
  • ›Building forms correctly is critical for a flat slab

Must-have tools

Concrete mixer or mixing tubTrowel and floatLevelSafety gloves + eye protection

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.
Can I pour concrete in cold weather?
Yes, but temps below 40°F slow curing significantly. Keep fresh concrete above 50°F for at least 7 days using insulated blankets. Don't pour when the ground is frozen — it cracks as the frost thaws.
What is a standard concrete mix ratio?
A general-purpose mix is 1 part cement : 2 parts sand : 3 parts gravel by volume (1:2:3). For high-strength work like footings, use 1:1.5:3. Bag mixes are pre-blended — check the bag for its designed PSI.

Common mistakes to avoid

  • ✕Not adding a waste buffer — fresh concrete can't be patched cleanly mid-pour. Add at least 10% to your calculated volume.
  • ✕Forgetting concrete sets faster in heat — above 80°F you may have 45 minutes of working time. Plan the pour sequence before mixing.
  • ✕Using the wrong bag weight — a 60 lb bag yields 0.45 cu ft; an 80 lb bag yields 0.60 cu ft. Mixing up bag sizes causes shortages mid-pour.
  • ✕Skipping control joints — without planned cuts or breaks every 8–12 ft, the slab will crack randomly.

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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 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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