Concrete Coverage Calculator

Calculate concrete volume, needed bags, and cubic feet instantly for 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, cubic feet and bag count

What it does – The Concrete Coverage Calculator takes the length, width and thickness of your slab and instantly converts them to cubic yards, cubic feet, and the number of 80‑lb bags of mix you’ll need. Why it matters – Knowing the exact volume prevents over‑ordering, saves money, and ensures you have enough material to finish without delays. How to read the results – Cubic feet is the raw volume; divide by 27 to see cubic yards, the standard unit for deliveries. Multiply cubic feet by 1 ÷ 0.6 (≈ 1.67) to get the bag count, then round up. All numbers are shown automatically, so you can copy them straight into your purchase order. You can also change any dimension and see how the material needs shift, perfect for comparing different slab thicknesses or adding a small allowance for spillage. The tool works on any device, no download required.

Pro tips

  • Add 5‑10% extra for waste and spillage
  • Round bag count up to the next whole bag
  • Order bags in multiples that match delivery truck capacities
  • Double‑check thickness units; inches vs. feet cause big errors

Real-life examples

  • A homeowner pouring a 12 ft × 10 ft patio 4 in thick
  • A contractor estimating concrete for a 30 ft × 20 ft warehouse floor 6 in thick
  • A DIYer planning a concrete driveway ramp with varying thickness

Case study

Mike needed a 10 × 8 ft patio 4 in thick. Using the calculator he saw he required 1.78 cubic yards, which translated to 10 bags. He ordered 10 bags, avoided a costly over‑order, and completed the patio on schedule.

Frequently asked questions

How many 80‑lb bags are needed for a 5 ft × 5 ft slab 3 in thick?
Enter the dimensions; the tool will show the exact bag count, rounding up to the next whole bag.
Why does the calculator show both cubic feet and cubic yards?
Cubic feet is the direct volume; cubic yards is the industry standard for ordering bulk concrete.
Can I use the calculator for a sloped surface?
Enter the average length, width and thickness; the result gives an approximate material estimate.
Do I need to include a waste factor?
Yes, add 5‑10% to the bag total to cover spillage and minor errors.
Is the bag yield of 0.6 cubic feet accurate for all mixes?
0.6 ft³ per 80‑lb bag is the typical yield for standard mixes; specialty mixes may vary.