How to use it
- Enter length (ft), width (ft), and thickness (in) of your slab.
- Click calculate to get cubic yards, bags, and cubic feet.
- Round bag counts up and add waste allowance before ordering.
Pour a concrete slab and you need three numbers: cubic yards for the supplier, bags if you're mixing on-site, and cubic feet for reference. This calculator turns your slab dimensions into all three instantly.
Enter length and width in feet, thickness in inches. The tool multiplies the area by the thickness converted to feet, then divides by 27 for cubic yards and by 0.6 for 80-lb bags. Cubic feet is the raw volume.
Why it matters: ordering too little means a cold joint mid-pour. Ordering too much wastes money. The bag count tells you exactly how many 80-lb mixes to buy if you're not using a truck delivery.
Read cubic yards as your ready-mix order quantity. Read bags as your on-site mix count. Always round up and add 5–10% waste — settling, over-excavation, and spillage eat into your total.
Pro tips
- Add 5–10% waste allowance for spillage and over-excavation.
- Round bag counts up — partial bags aren't sold.
- Order 10–15% extra for truck delivery to avoid a cold joint.
- Double-check thickness — a 1-inch error changes volume significantly.
Real-life examples
- Pouring a 12×12 patio pad and needing bag count for a weekend DIY mix.
- Ordering a foundation footing from a ready-mix supplier by cubic yard.
- Estimating material for a garage floor repair before calling a contractor.
Case study
A homeowner needed a 10×10×4-in shed base. Guessing, they ordered 60 bags — came up 16 short. After using the calculator, they got 80 bags exactly, mixed on schedule, and finished in one day. No mid-pour panic, no wasted trips to the depot.