Pre-Mixed Concrete Bags Needed
Optional Cost Estimate
I Already Have Concrete Bags — How Much Can I Pour?
Reverse the calculation using the approximate bag yield. Useful if you already bought or have leftover bags.
How Much Concrete Do I Need?
For a rectangular slab or footing, multiply length × width × depth in feet to get cubic feet, then divide by 27 for cubic yards. For a round column or post hole, the calculator uses the cylinder formula π × radius² × height. The waste allowance is then added to the exact volume.
Concrete bag yields
Bag estimates use approximate QUIKRETE Concrete Mix yields: 40 lb = 0.30 ft³, 60 lb = 0.45 ft³ and 80 lb = 0.60 ft³. Always check the yield printed on the specific product you buy.
Waste allowance
A 10% starting allowance is provided because real pours can use more material than ideal dimensions suggest. Increase or reduce it for your project conditions.
Bags or ready-mix?
Bagged mix can be practical for smaller pours, while larger jobs may be easier with ready-mix delivery. Local minimum orders, delivery fees, access and labor can change the best choice.
Concrete Calculator FAQ
How many cubic feet are in one cubic yard?
One cubic yard contains 27 cubic feet.
How many 80 lb bags of concrete make a cubic yard?
At an approximate yield of 0.60 cubic feet per 80 lb bag, one cubic yard requires about 45 bags before any extra waste allowance.
Why should I order extra concrete?
Excavation, uneven subgrade, form variation and spillage can make the actual amount needed greater than the ideal geometric volume. This calculator defaults to 10% extra, but the appropriate allowance depends on the job.
Can I use this for structural design?
This tool estimates material volume only. It does not determine structural thickness, reinforcement, footing size, concrete strength or code compliance. Those requirements depend on the project and local conditions.