How to use it
- Enter length in feet
- Enter width in feet
- Enter thickness in inches
- Read cubic yards, bags, and cubic feet
This calculator determines the exact volume of concrete needed for slabs, patios, and footings based on three measurements: length, width, and thickness. Enter dimensions in feet and inches, and the tool instantly returns cubic yards, cubic feet, and the number of 80-lb bags required—each bag yielding 0.6 cubic feet. Knowing the precise volume prevents costly over-ordering or dangerous shortages on site. The cubic yard figure helps contractors coordinate deliveries, while the bag count lets small-job builders shop confidently at the supply yard. Always round up bags to the nearest whole number and add 5–10% waste for spillage and over-excavation. Check local delivery minimums before placing orders. Use the results to budget accurately, schedule crews, and avoid project delays caused by material shortages. A 10 ft × 10 ft slab at 4 inches thick requires roughly 1.23 cubic yards or 56 bags—useful for quick mental checks before you start.
Pro tips
- Add 5–10% waste allowance for spillage
- Round bag count up to whole bags
- Check concrete delivery minimums
- Double-check thickness—confusing inches and feet is a common mistake
Real-life examples
- Pouring a backyard patio slab
- Setting fence post footings
- Repairing a garage floor patch
Case study
Mike needed a 12×12 shed pad at 4 inches thick. He estimated 2 yards by eye and ordered too much, wasting $90. Using the calculator, he got 1.78 cubic yards and 72 bags, ordered exactly right, and saved money while finishing on schedule.