How to use it
- Enter the slab length in feet.
- Enter the width in feet.
- Enter the thickness in inches.
- Hit Calculate to see cubic yards, cubic feet, and 80-lb bag count.
This calculator tells you exactly how much concrete you need for a slab, walkway, or footing. Enter length, width, and thickness, and it returns cubic yards, cubic feet, and the number of 80-lb bags. Why it matters: ordering too little means a second pour and a cold joint; ordering too much wastes money. The result uses a standard 80-lb bag covering about 0.6 cubic feet, so you can round up for waste. Read it this way: cubic yards is what you'll order from a ready-mix plant; cubic feet helps you compare; bags are for DIY pours. For example, a 10-ft by 10-ft slab at 4 inches thick comes to about 1.23 cubic yards or 56 bags. Use the numbers to plan your order and avoid trips to the store.
Pro tips
- Add 5–10% waste — round bag counts up to the next full bag.
- For ready-mix, order by the cubic yard and round up to avoid a short load.
- Don't forget to account for gravel base or rebar; the calculator covers concrete only.
- Double-check thickness in inches — a 4-inch slab vs 6-inch changes yardage significantly.
Real-life examples
- Poured a 10x12 patio slab and need to know how many 80-lb bags to haul.
- Building a 4-inch thick sidewalk along the driveway and want ready-mix yardage.
- Filling sonotubes for deck footings and need exact bag count per tube.
Case study
Before, Mark guessed and ended up mixing an extra half-yard. After using the calculator for his 10x10 slab, he ordered exactly 56 bags, finished in one pour, and returned nothing. No extra trips, no leftover concrete.