Concrete bag calculator
This turns a volume into a bag count using the yield you set. Real coverage shifts with the mix and how you finish it, so keep a spare bag or two on hand rather than trusting the tally to the last unit. It does not decide how thick or how strong the pour needs to be — that is your plans' job.
Enter a known volume, or the length, width and thickness to have the tool work the volume out, then set the yield your bag prints. The result is the bag count for the job — the raw figure and the rounded-up number you actually carry to the till.
Worked example
Say you need half a cubic yard. That is 0.5 × 27 = 13.5 cubic feet. At 0.6 ft³ per 80 lb bag that is 13.5 ÷ 0.6 = 22.5 bags; add 10% for waste and round up and you would buy 25. Switch to 60 lb bags at 0.45 ft³ each and the same volume needs 30 before waste.
The formula
bags = (volume in ft³ × (1 + waste)) ÷ yield per bag, rounded up
Get the volume into cubic feet — a cubic yard is 27 of them, or measure length × width × thickness directly — then divide by what one bag yields once mixed. The waste margin covers spillage and an uneven base, and rounding up is simply because you buy whole bags.
What this tool assumes
That a cubic yard is 27 cubic feet — a definition. The yield per bag and the waste are yours to set, because the bag's printed figure and your site conditions are the two things that genuinely move the count.
Questions
- How many bags of concrete make a cubic yard?
- About 45 of the 80 lb size. A mixed 80 lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet, so 27 ÷ 0.6 ≈ 45. A 60 lb bag makes about 0.45 cubic feet, so a yard is closer to 60 of those. The yield is an editable field here — set it to whatever your bag prints.
- Should I enter a volume or the dimensions?
- Whichever you already have. If a supplier or another calculator told you the yardage, type that in the volume box. If all you have is a pad or trench to measure, switch to dimensions and give the length, width and thickness — the tool works out the volume for you and then the bag count.
- How accurate is the bag yield?
- The 0.6 ft³ per 80 lb bag figure is a common, honest average, but brands and mixes differ and a stiffer or wetter mix changes it slightly. The number the bag itself states beats any default, so overwrite it. Because the yield is the biggest lever on the count, getting it right matters more than the last decimal on your measurements.
- When is bagging not worth it?
- Once the tally climbs past roughly ten bags, the mixing time and the cost usually tip toward ready-mix by the yard. The tool will happily count a hundred bags for you, but treat a three-figure result as a nudge to price a truck instead — your back will thank you.
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