How to use it
- Enter slab length in feet.
- Enter slab width in feet.
- Enter slab thickness in inches.
- Read your total cubic feet, cubic yards, and required 80-lb bags.
Short pours ruin concrete projects. If you under-order, cold joints weaken your foundation. If you over-order ready-mix, you throw money down the chute. This calculator converts your slab length, width, and thickness into exact cubic feet, cubic yards, and 80-lb bags.
Use the results to choose the most cost-effective supply method. For pours under one cubic yard, buying pre-mixed 80-lb bags (yielding 0.6 cubic feet each) usually saves money and gives you total schedule control. For larger slabs, use the cubic yards readout to order bulk ready-mix delivery from your local batch plant.
Review your numbers, add your buffer for uneven subgrade or spillage, and order with absolute confidence before the first truck leaves the plant.
Pro tips
- Add 10% to your total order to account for uneven subgrade depth and spillage.
- Always round up to the next full 80-lb bag; a partial bag shortfall halts your entire finish.
- Check ready-mix truck minimum order fees; small orders often carry an extra short-load charge.
- Measure your formwork depth across multiple points to verify the true thickness before pouring.
Real-life examples
- Pouring a 10x10 foot backyard patio pad to hold an outdoor kitchen or hot tub.
- Forming a 4-inch thick concrete walkway connecting your driveway to the backyard gate.
- Setting a reinforced concrete slab base for a detached storage shed or workshop.
Case study
Mark framed a 12x16 shed slab 4 inches deep. Instead of guessing bag counts, he calculated his exact volume: 64 cubic feet, or 2.37 cubic yards. Realizing that required 107 eighty-pound bags, he skipped hand-mixing and ordered 2.75 yards from a ready-mix truck. The pour finished in two hours with zero cold joints and no wasted bags.