How to use it
- Enter the slab or trench length in feet.
- Enter the width in feet.
- Enter the planned slab thickness in inches.
- Read your exact volume in cubic yards, cubic feet, and 80-lb bags.
Under-ordering concrete halts your job and creates structural cold joints. Over-ordering wastes hundreds of dollars on unreturnable mix. This calculator eliminates guesswork by converting your project's length, width, and thickness into exact cubic feet, cubic yards, and 80-lb pre-mixed bags.
Use the results to choose your buying method. If your project requires small volumes, read the bag count—calculated at 0.6 cubic feet per standard 80-lb bag—to know precisely what to haul from the store. If your pour exceeds one cubic yard (27 cubic feet), order ready-mix concrete by the cubic yard from a local batch plant.
Always check your measurements before purchasing. Having exact volume data protects your budget, prevents mid-pour shortages, and ensures a clean, single-pour structural finish.
Pro tips
- Add 10% extra volume to your order to account for uneven subgrade depth, spillage, and form deflection.
- Always round up to the nearest full bag or quarter-yard; suppliers do not sell partial batches.
- Check your ready-mix supplier's minimum load fee; orders under 4 or 5 yards often incur short-load charges.
- Measure slab thickness across several excavated points; digging just 0.5 inches too deep demands roughly 12% more concrete.
Real-life examples
- Pouring a 10x10-foot, 4-inch backyard patio slab and deciding between truck delivery or bagged mix.
- Forming a 3-foot wide, 4-inch thick walkway to budget the exact number of 80-lb bags needed.
- Pouring a garage floor or shed foundation to submit accurate yardage specs to a ready-mix dispatcher.
Case study
Mark needed to pour a 12x20-foot patio slab at 4 inches thick. Instead of guessing, he calculated his exact volume: 2.96 cubic yards (80 cubic feet, or 134 bags of 80-lb mix). He added 10% for uneven subgrade and ordered 3.25 yards from a ready-mix supplier, finishing the pour smoothly with zero emergency store runs.