Calculate How Much Concrete Calculator

Instantly calculate how many cubic yards, cubic feet, and 80‑lb bags of concrete you need for any slab—free and instant.

  • Free
  • No sign-up
  • Instant results

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How to use it

  1. Enter length, width, and thickness in the fields provided.
  2. Press the Calculate button.
  3. Read the cubic‑feet total, the cubic‑yard conversion, and the bag count.

What this tool does

It takes the dimensions you input—length (ft), width (ft) and thickness (in)—and instantly returns three useful figures:

  • Cubic feet of concrete required (the raw volume).
  • Cubic yards (the industry‑standard unit for ordering bulk concrete).
  • Number of 80‑lb bags (useful for small DIY pours).

Why it matters

Knowing the exact volume prevents over‑ordering, which saves money, and under‑ordering, which avoids project delays.

How to read the results

  • Cubic feet is the direct calculation of space.
  • Cubic yards is cubic feet divided by 27.
  • Bags is cubic feet divided by 0.6 (each bag yields 0.6 ft³).
    Use these numbers to place accurate orders with your supplier.

Pro tips

  • Add 5‑10% extra for waste and spillage.
  • Round up bag count to the nearest whole bag—partial bags aren’t sold.
  • Order concrete a day before the pour to ensure fresh mix.
  • Double‑check thickness; a common mistake is entering inches as feet.

Real-life examples

  • A homeowner pouring a 4 × 8 ft patio slab 4 in thick.
  • A contractor estimating material for a 12 × 20 ft garage floor.
  • A landscaper calculating concrete for a small garden path.

Case study

Mike needed a 6 × 10 ft patio at 3 in thickness. Using the calculator he saw he required 1.33 cubic yards, which equals 22 bags. He ordered exactly that amount, avoided a costly over‑order, and completed the patio on schedule.

Frequently asked questions

How do I convert the result to cubic yards?
Divide the cubic‑feet total by 27; the calculator does this automatically.
Why does the bag count seem high?
Each 80‑lb bag only fills 0.6 ft³, so more bags are needed for larger volumes.
Do I need to include a waste factor?
Yes, add 5‑10% to the cubic‑feet result to cover spillage and variations.
Can I use metric units?
This tool is US‑focused; convert your metric measurements to feet and inches first.
What if my slab isn’t a perfect rectangle?
Break the area into rectangular sections, calculate each, then sum the results.