How to use it
- Enter your pour's length and width in feet.
- Enter the planned slab thickness in inches.
- Read your required material volume in cubic yards, cubic feet, and 80-lb bags.
Pouring concrete leaves zero room for guesswork. Run short mid-pour, and you get a cold joint that ruins structural integrity. Buy too much, and you waste cash on heavy bags you cannot return. This calculator eliminates that risk instantly. Enter your length, width, and thickness to get three mission-critical numbers: total cubic feet, total cubic yards, and the exact count of standard 80-lb bags needed based on their 0.6-cubic-foot yield. Use cubic yards when scheduling a ready-mix truck for large pours like driveways or garage slabs. Use the bag count if you are mixing by hand or renting a mixer for smaller jobs like footings, shed pads, or walkways. You get the exact volume required for the void, letting you budget materials accurately and schedule the right delivery method before work begins.
Pro tips
- Always add 10% to your total volume for spillage, subgrade unevenness, and formwork deflection.
- Round up partial bag counts to the next whole unit; home improvement stores do not sell half-bags.
- Order a ready-mix truck once your project exceeds 1 cubic yard (45 bags) to save significant labor.
- Measure the actual excavation depth across multiple points, not just the height of the outer forms.
Real-life examples
- Pouring a 4-inch patio slab to find whether a ready-mix truck is cheaper than bags.
- Setting fence posts or deck footings and buying the exact number of 80-lb bags.
- Extending a concrete driveway and ordering precise yardage from the supplier.
Case study
Mark planned a 10x12-foot shed slab at 4 inches thick. Instead of guessing 30 bags, he ran the numbers: 40 cubic feet, or 67 bags (80-lb). He ordered 74 bags to account for waste. His pour finished flush with zero cold joints and zero emergency supply runs.