Concrete Slab Volume and Bags Calculator
Enter your slab's length, width and thickness to calculate the concrete volume needed and roughly how many bags to buy.
Concrete Slab Volume and Bags Calculator
Calculates the concrete volume needed for a slab and how many bags of pre-mixed concrete that requires.
This calculator multiplies slab length, width and thickness to get the required concrete volume, then divides by your bag's stated yield to estimate how many pre-mixed bags you'll need. Because bag yields vary by brand and bag size, the yield is left as an adjustable input rather than a fixed constant — check your specific bag's packaging for its cubic-meter (or convert from cubic-foot) yield before buying. Always round the bag estimate up and add a small waste margin for a real pour.
Example
- With the default values shown above, this calculator returns: Concrete Volume Needed ≈ 2 m³; Bags Needed (approx.) ≈ 160 bags.
Frequently Asked Questions
Should I round the bag count up?
Yes — always round up to the next whole bag, and buy a small extra margin (5-10%) for spillage, uneven subgrade and waste.
Where do I find my bag's yield?
Bag packaging typically states the yield in cubic feet or liters per bag; convert that to cubic meters, or check the manufacturer's spec sheet, and enter it as the bag yield above.
Sources
- Standard formula, publicly documented method