Cement and sand ratio calculator

Fresh mortar and plaster shrink as water fills the gaps between grains, which is why the wet volume is multiplied by a dry-volume factor before splitting. Cement mass assumes 1440 kg per cubic metre; bag counts round up with wastage, sand scales with wastage, and water comes from the water-cement ratio times the cement mass. This sizes an ordering list, not a mix design: strength and workability depend on the sand grading and the water you actually add, so follow the spec your structural details call for.