How to use it
- Enter the slab length in feet.
- Enter the slab width in feet.
- Enter the thickness in inches.
- Get cubic yards, cubic feet, and 80-lb bag count.
This calculator turns your slab dimensions into the exact concrete volume you need — no guesswork. It shows cubic yards for ordering ready-mix, cubic feet for reference, and the number of standard 80-lb bags for DIY projects. Each 80-lb bag yields 0.6 cubic feet, so the bag count is always accurate. For instance, a 10×10 slab at 4 inches thick is about 1.23 cubic yards and needs roughly 56 bags. Why does this matter? Ordering too little means a rushed trip to the store; ordering too much wastes money. Use the results to compare ready-mix vs. bagged concrete, budget accurately, and avoid delays. The thickness input is in inches, so you don't have to convert anything. Whether you're setting posts, pouring a small slab, or patching a walkway, this tells you exactly what to buy.
Pro tips
- Add 5–10% for waste, spillage, or uneven subgrade.
- Round bag count up to the nearest whole bag — never down.
- For large slabs, buy in bulk or get a ready-mix quote — it's often cheaper.
- Double-check that thickness is in inches, not feet, before calculating.
Real-life examples
- Pouring a small patio and need to know how many bags of mix to buy.
- Setting fence posts and estimating concrete for the holes.
- Planning a concrete walkway repair and comparing bagged vs. delivered concrete.
Case study
Mark needed a 12×8 slab at 4 inches thick. He entered the numbers, saw 1.19 cubic yards and 53 bags, then ordered 56 to cover waste. He finished the pour without a second trip — saving hours and a rental truck.