Concrete Mix Design Calculator

This calculator splits total aggregate weight into fine and coarse portions using a ratio that depends on aggregate shape: 42% fine for rounded gravel versus 38% fine for crushed stone. Angular crushed stone particles interlock with each other more effectively than smooth rounded gravel, which naturally fills more of the voids between coarse particles and reduces how much sand is needed to fill the remaining gaps.

The calculator uses Abrams' law, fc = A/B^(w/c), with A≈14,000 and B≈4, so estimated strength rises sharply as the water-cement ratio drops — this captures the well-established relationship that less water per unit of cement produces a denser, stronger paste. It's a simplified empirical fit, though, not a substitute for actual trial-batch testing, since real strength also depends on cement type, curing conditions, and admixtures that this formula doesn't take into account.

27 cubic feet equals one cubic yard, and this calculator's inputs (cement content, water-cement ratio) are all specified per cubic yard of concrete. The yield check sums the volumes of cement, water, fine aggregate, coarse aggregate, and assumed 5% entrained air using each material's specific gravity — if that sum lands far from 27 ft³, it's a signal that the assumed total concrete weight of 3,950 lb/yd³ doesn't match your actual mix proportions well.

It works from three simplified inputs — target strength, water-cement ratio, and cement content — using fixed assumptions like 3,950 lb/yd³ total concrete weight and 5% entrained air, and it doesn't account for aggregate moisture content, chemical admixtures, or slump/workability requirements. A production mix design also needs lab trial batches to confirm strength and yield, since Abrams' law here is an approximation, not a measured result.