Calculate cement, sand, and aggregate quantities for a target concrete volume and mix ratio.
A concrete mix ratio expresses the proportion of cement to sand to coarse aggregate by volume — a 1:2:4 mix means for every 1 part cement, use 2 parts sand and 4 parts aggregate.
This is different from a pure volume calculator (which tells you how much total concrete you need for a slab): this tool tells you how to split that total volume into raw material quantities to mix it yourself.
The ratio you choose affects strength — richer mixes (more cement relative to aggregate, like 1:1:2) cost more but cure stronger, appropriate for structural elements rather than a garden path.
27 cu ft of concrete at a 1:2:4 ratio splits into 3.86 cu ft cement (about 3.1 bags), 7.71 cu ft sand, and 15.43 cu ft aggregate.
1:2:4 (general purpose) is standard for driveways and sidewalks. Reserve 1:1:2 for structural work like footings or load-bearing elements.
No — water-to-cement ratio is a separate consideration, typically around 0.4-0.6 by weight of cement, and affects workability and final strength independently of the aggregate ratio.
In the US, a standard bag is 94 lb (42.6 kg) and occupies roughly 1.226 cubic feet loose — that conversion is what this calculator uses to estimate bag count.