How to use it
- Enter the length of your slab or area in feet.
- Enter the width in feet.
- Enter the thickness in inches.
- Click Calculate to see cubic yards, total cubic feet, and number of 80-lb bags.
This calculator tells you exactly how many 80-lb bags of concrete mix to buy for your project. Each standard 80-lb bag yields about 0.6 cubic feet, so the tool converts your slab dimensions into cubic feet, then into bags and cubic yards.
Why it matters: guessing leads to too much leftover concrete or a shortfall mid-pour. With exact bag counts, you can order confidently, avoid extra trips to the store, and keep your pour moving before the mix sets.
Reading the results: cubic yards is the standard unit for ready-mix, but since you're using bags, focus on the bag count. Cubic feet helps you double-check if you're using a different bag size. The numbers are precise — round up when you order to cover small errors and waste.
Use it for patios, footings, walkways, fence posts, and any slab. Adjust thickness to match your project, and you'll know exactly what to buy.
Pro tips
- Add 5–10% extra to the bag count for waste, spillage, or slight depth variations.
- Round up to the nearest whole bag — you can't order a fraction of a bag, and leftover dry mix stores well.
- Order all bags at once from the same batch to keep color consistent if you're doing multiple pours.
- Don't measure in inches by mistake — always convert thickness to feet or use the calculator's unit field correctly.
Real-life examples
- Planning a 10x10 patio slab and need to know how many bags to haul.
- Estimating concrete for fence post footings before digging holes.
- Calculating a 3-inch-thick walkway pour without overbuying mix.
Case study
Marco needed a 12x4 ft walkway at 4 inches thick. He guessed 30 bags. Using this calculator, he saw the volume was 16 cubic feet and needed 27 bags — saving 3 bags of mix and a trip to return extras. His pour finished on time with no waste.