How many concrete bags do I need?
First calculate the project volume in cubic feet, add any waste allowance, then divide by the approximate yield per bag.
Approximate bag yields
This calculator uses approximate yields of 0.30 ft³ for 40 lb, 0.375 ft³ for 50 lb, 0.45 ft³ for 60 lb and 0.60 ft³ for 80 lb bags.
Actual yield can vary by manufacturer and product. Use package specifications for final purchasing.
Frequently asked questions
Why round up the number of bags?
You cannot usually purchase a fraction of a bag, so the result is rounded up.
Do all 80 lb concrete bags have the same yield?
No. Product yield can vary slightly, so manufacturer specifications should be checked.
Should I include waste?
Adding some extra can help cover uneven forms, spills and mixing loss.
Using this calculator effectively
The concrete bag calculator estimates how many premixed bags are needed for a rectangular pour using an approximate yield per bag size. It is best suited to smaller jobs where bagged mix is more practical than ready-mix delivery.
Common uses
- Estimating bagged concrete for small pads and repairs.
- Comparing 40, 50, 60 and 80 lb bag quantities.
- Adding a waste allowance before purchasing material.
Tips for a better estimate
- Check the actual yield printed on the bag because products vary by manufacturer.
- Round the final quantity up to whole bags.
- For large pours, compare bagged material with ready-mix volume and logistics before deciding how to supply the job.
Related calculations
Concrete Calculator · Concrete Slab Calculator · Concrete Driveway Calculator