Concrete Bag Calculator
Estimate the number of 40 lb, 60 lb or 80 lb concrete bags for a rectangular slab or pour, including a waste allowance.
Project details
Estimate
Typical planning yields used here are 0.30 ft³ for 40 lb, 0.45 ft³ for 60 lb and 0.60 ft³ for 80 lb bags. Always verify the yield printed on the actual product.
How bag quantity is estimated
The calculator converts slab thickness from inches to feet, finds the cubic-foot volume, adds your waste allowance, then divides by the estimated yield of each bag size. Bag quantities are rounded up because partial bags are not normally purchased.
When should I use bagged concrete?
Bagged mix is convenient for small slabs, steps, repairs, footings and post holes. For larger pours, compare the bag count with local ready-mix delivery pricing and minimum-order requirements.
Concrete bag FAQ
How many 80 lb bags make a cubic yard?
Using a planning yield of 0.60 cubic feet per bag, one cubic yard is about 45 bags before adding project waste.
Why does the calculator round up?
Concrete mix is sold in whole bags, so the result rounds up to avoid planning for a fraction of a bag.
Should I use the yield on the bag?
Yes. Product yields can vary, so the manufacturer's stated yield is the best value for a final purchase estimate.