Enter a volume and mix ratio to calculate cement bags, sand, and aggregate quantities.
How to Use the Concrete Mix Calculator
Enter the volume of finished (wet) concrete you need, then set a cement:sand:aggregate ratio — 1:2:4 is the default, but the three fields are yours to change. Cement bags, sand, and aggregate volumes appear together below.
Dry ingredients take up more room than the concrete they become, because loose sand and gravel have air gaps between the particles that disappear once everything's mixed and compacted. Concrete mix design accounts for this with a dry volume factor — 1.54 is the standard figure — applied before the ratio splits the total three ways:
dry volume = wet volume × 1.54
cement volume = dry volume × (cement part ÷ total parts)
sand volume = dry volume × (sand part ÷ total parts)
aggregate volume = dry volume × (aggregate part ÷ total parts)Cement bag count assumes a standard 94 lb (US) bag, which holds about 1.25 cu ft of loose cement. A 1:2:4 ratio is a reasonable general-purpose mix for footings and slabs on grade; go richer (1:1.5:3) for higher-strength structural work, or leaner (1:3:6) for mass fill where strength matters less than volume.
These are nominal mix ratios by volume, not a substitute for a structural engineer's mix design on anything load-bearing or safety-critical.