Concrete Sq Ft Calculator

Calculate concrete needed in cubic yards, bags, and cubic feet instantly and free.

  • Free
  • No sign-up
  • Instant results

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How to use it

  1. Enter length in feet
  2. Enter width in feet
  3. Enter thickness in inches
  4. Read cubic yards, bags and cubic feet results

What it does – The Concrete Sq Ft Calculator takes the length, width and thickness you enter and instantly shows three useful measures: total volume in cubic yards, the number of 80‑lb bags required, and the volume in cubic feet. Why it matters – Knowing cubic yards helps you order the right amount of ready‑mix, while bag count lets you buy bagged mix without over‑paying for excess. How to read – One cubic yard equals 27 cubic feet; the bag count is derived from the fact that each 80‑lb bag yields about 0.6 cubic feet. You can save time by entering the dimensions of patios, driveways, sidewalks, or foundation slabs, and the calculator instantly converts them to the units contractors use. The output lets you add a safety margin or adjust for irregular shapes before placing an order.

Pro tips

  • Add 5‑10% extra for waste and spillage
  • Round up bag count to the next whole bag
  • Compare prices per cubic yard, not per bag
  • Double‑check thickness conversion from inches to feet

Real-life examples

  • Estimating concrete for a new driveway slab
  • Planning material for a backyard patio renovation
  • Sizing mix for a foundation footings project

Case study

Mike needed to pour a 12 × 8 ft patio 4 in thick. Using the calculator he saw he required 1.6 cubic yards, which translated to 3 bags of mix. He ordered exactly that amount, avoided a $150 over‑order, and completed the patio on schedule.

Frequently asked questions

How many 80‑lb bags are needed for 1 cubic yard?
One cubic yard is 27 cubic feet; divide 27 by 0.6 to get about 45 bags.
Can I use the calculator for metric measurements?
Enter the dimensions in feet and inches; the tool converts to cubic yards and bags using US units.
Should I add extra concrete for a slab?
Yes, add a 5‑10% waste allowance to the calculated volume.
What if my slab isn’t a perfect rectangle?
Calculate each rectangular section separately and sum the results.
Is the bag count rounded up automatically?
The calculator shows the exact decimal; round up to the next whole bag when ordering.