How to use it
- Enter length in feet.
- Enter width in feet.
- Enter thickness in inches.
- Read cubic yards, cubic feet, and bag estimate instantly.
What it does – The calculator turns the dimensions of your slab (length, width, thickness) into three useful quantities: total cubic feet, equivalent cubic yards, and the number of standard 80‑lb bags needed. Knowing the cubic yards helps you order the right amount of ready‑mix, while the bag count tells you how many bags of dry mix to purchase for smaller jobs. The results appear instantly, so you can compare options, budget, and avoid costly over‑orders. Read the cubic‑feet line for the raw volume, the cubic‑yard line for ready‑mix orders (1 yd = 27 ft³), and the bag line using the 0.6 ft³ per bag conversion. No math required – just plug in your numbers. You can also adjust for a 5% waste factor by increasing the bag total, ensuring you have enough material even if cuts or spillage occur.
Pro tips
- Add 5‑10% extra for waste and breakage.
- Round up bag count to the next whole bag.
- Order ready‑mix in full‑yard increments; suppliers often charge per yard.
- Double‑check thickness conversion (inches ÷ 12 = feet) before entering.
Real-life examples
- Homeowner estimating concrete for a 12 ft × 12 ft patio, 4 in thick.
- Contractor planning a 20 ft × 30 ft garage floor, 6 in thick.
- DIYer figuring material for a 6 ft × 8 ft garden stepping stone base, 3 in thick.
Case study
Mike needed a 10 ft × 15 ft slab 5 in thick for his workshop. Using the calculator, he saw the job required 2.2 cubic yards, or about 37 bags. He ordered exactly that amount, avoided a $150 over‑order, and completed the pour on schedule.