How to use it
- Enter the total length of your pour area in feet.
- Enter the width of your pour area in feet.
- Enter the slab or footing thickness in inches.
- Read your total volume in cubic feet, cubic yards, and required 80-lb bags.
Running out of wet concrete mid-pour ruins slabs and creates weak cold joints. Ordering too much wastes hard cash. This calculator converts your project dimensions directly into cubic feet, cubic yards, and standard 80-lb bags.
Read your results based on your procurement method. For smaller projects like fence posts or walkways under 1 cubic yard, use the bag count. The calculation is based on standard 80-lb bags yielding about 0.6 cubic feet each. For large pours like driveways, patios, or foundations, reference cubic yards to order ready-mix transit trucks.
Cubic feet gives you the raw physical volume before packaging constraints. Having all three numbers upfront allows you to walk into a supply yard or call a ready-mix dispatcher with complete certainty, eliminating guesswork, delayed work schedules, and expensive second-delivery fees.
Pro tips
- Add 10% extra volume to cover uneven subgrades, spillage, and form spreading.
- Always round up to the nearest full bag; you cannot purchase fractional bags.
- Switch from bagged concrete to a ready-mix truck when your project exceeds 2 cubic yards.
- Measure trench depth at multiple points to capture true depth variations before calculating.
Real-life examples
- Pouring a 10x10 foot backyard patio slab at 4 inches thick.
- Calculating exact 80-lb bag counts for setting fence and deck posts.
- Ordering ready-mix concrete by the cubic yard for a driveway extension.
Case study
Mark planned a 12x20 foot garage apron at 4 inches thick. Instead of guessing, he ran the numbers. The tool calculated 80 cubic feet, or 134 bags (80-lb) yielding 0.6 cubic feet each—roughly 3 cubic yards. He ordered a ready-mix truck instead of hand-mixing 134 bags, saving a weekend of hard labor and $240 in partial-load fees.
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