How to use it
- Enter length in feet
- Enter width in feet
- Enter thickness in inches
- Read cubic feet, yards and bag count
Enter the slab’s length, width and thickness, and the calculator instantly converts those dimensions into three practical figures: total cubic feet of concrete, cubic yards for ordering, and the number of 80‑lb bags you’ll need. Knowing the cubic‑foot volume lets you compare different slab sizes, while cubic yards are the unit most suppliers use for delivery quotes. The bag count is based on the standard yield of 0.6 ft³ per 80‑lb bag, so you can see exactly how many bags to purchase without over‑ordering. For example, a 12 ft × 10 ft slab that’s 4 in thick equals 40 ft³, which translates to about 1.5 yd³ and 67 bags. Use the results to budget, schedule deliveries, and avoid costly material waste. You can also adjust the dimensions to test different design options or factor in a small overage for spillage.
Pro tips
- Add 5‑10% extra for waste and spillage
- Round bag count up to the next whole bag
- Order using the cubic‑yard figure; suppliers may have minimum loads
- Double‑check thickness conversion from inches to feet
Real-life examples
- Homeowner planning a 6‑ft‑by‑8‑ft patio 4 in thick
- Contractor estimating concrete for a garage floor 20 ft × 22 ft × 5 in
- DIY landscaper sizing a garden pathway 2 ft wide, 12 ft long, 3 in thick
Case study
Mike needed a 12 ft × 15 ft driveway 4 in thick. Using the calculator he saw the job required 60 ft³, about 2.2 yd³ and 100 bags. He ordered exactly that, saved $200 on excess material, and the pour finished on schedule.