Calculate cement bags, sand and aggregate volume needed for a concrete or mortar mix, based on your target mix ratio (like 1:2:4) and the volume you need to fill.
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Our Concrete Calculator estimates bags of pre-mixed concrete (like standard 40/60/80 lb bags) by their weight yield, the simplest approach when buying pre-mixed bags. This calculator instead works from a raw mix ratio, cement to sand to aggregate, like the common 1:2:4 general-purpose ratio, the approach used when mixing concrete or mortar from separate raw materials rather than a single pre-mixed bag.
Loose dry materials (cement, sand, aggregate) take up more space than they do once mixed with water and compacted, because dry particles have air gaps between them that close up during mixing. This calculator applies a standard bulking factor of 1.54 to convert your target finished (wet) volume into the total dry material volume you need to start with, then splits that dry volume across your mix ratio.
For a 10 ft × 10 ft slab, 4 inches thick, with a 1:2:4 (cement:sand:aggregate) mix ratio: wet (finished) volume = 10 × 10 × (4 ÷ 12) ≈ 33.33 cubic feet. Dry volume = 33.33 × 1.54 ≈ 51.33 cubic feet. With 7 total parts (1+2+4), cement gets 1/7 of that: 51.33 ÷ 7 ≈ 7.33 cu ft, rounded up to 8 bags (each 94 lb bag ≈ 1 cu ft). Sand gets 2/7: 51.33 × (2/7) ≈ 14.67 cu ft. Aggregate gets 4/7: 51.33 × (4/7) ≈ 29.33 cu ft.
Using the wet (finished) volume directly to buy dry materials, dry cement, sand and aggregate take up more space loose than once mixed and compacted, this calculator's 1.54 bulking factor accounts for that gap, skipping it would under-order materials.
Using a mix ratio meant for a different application without checking it's appropriate, 1:2:4 suits many general-purpose, non-structural uses, but load-bearing work typically needs a stronger ratio like 1:1.5:3, verify against project specs or an engineer's guidance for anything structural.
Forgetting this calculator doesn't estimate water, water quantity depends on the desired water-cement ratio for the required strength and workability, and needs to be worked out separately from this dry-material bulking calculation.
1:2:4 (cement:sand:aggregate) is a commonly used general-purpose ratio for many non-structural applications. Ratios like 1:1.5:3 are used for higher-strength applications, and 1:3:6 for lower-strength, less critical work. Check project specifications or a structural engineer's guidance for anything load-bearing.
94 lb is the standard weight of a full bag of Portland cement in the US, yielding approximately 1 cubic foot of loose cement material, the figure this calculator uses to convert cement volume into a bag count.
No, water quantity depends on the desired water-cement ratio for your specific strength and workability needs, and isn't part of the dry volume bulking calculation, consult mix design guidance for the correct water quantity for your ratio.
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