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Material Calculators That Get It Right

Enter your dimensions. Get exact bag counts, cubic yards, and cost estimates — instantly.

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Concrete Slab Calculator

Bag count, cubic yards, and cost estimate for any slab size.

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All Calculators

Concrete Slab Bags · Yards · Cost Concrete Footing Volume · Cost Gravel Driveway Tons · Yards Mulch Bags · Coverage Brick & Block Count · Area

How It Works

1
Enter dimensions Enter length, width, and thickness.
2
Set your prices Enter your local material costs and waste factor.
3
Get your numbers Bag count, cubic yards, cost, and a recommendation.

Quick Answers

How many bags of concrete do I need for a 10×10 slab? A standard 10×10 slab at 4 inches thick needs about 82 bags of 60 lb mix or 62 bags of 80 lb mix. How many bags of concrete do I need for a 12×12 slab? A 12×12 slab at 4 inches thick needs about 118 bags of 60 lb mix or 88 bags of 80 lb mix. How many bags of concrete do I need for a 20×20 slab? A 20×20 slab at 4 inches thick needs about 4.94 cubic yards — or roughly 326 bags of 60 lb mix. Ready-mix is recommended at this volume. Should I use bagged concrete or ready-mix? Bagged is best for pours under 1 cubic yard. Above that, ready-mix is faster, cheaper per yard, and more consistent. The slab calculator tells you which to use for your specific dimensions.

Why BuildCalc

  • Uses standard industry formulas
  • No account, no email, no upsell
  • Works on your phone on-site
  • Results in under 3 seconds
  • Built for real projects, not demos