SiteMathTools is a free set of construction material calculators for contractors, estimators, civil engineering students and DIY builders.
On site, miscalculation is expensive in both directions. Over-order and the surplus eats the margin; under-order and the job stops while someone drives to the merchant. Most estimating tools are either behind a paywall or too simplistic to trust for real work, so people fall back on rules of thumb.
Every calculator uses industry-standard formulas rather than approximations: the 1.54 dry-volume factor for concrete, D²/162 for rebar weight, and true volumetric subtraction for mortar. Where a constant is open to interpretation, we use the common published value and show the working so you can check it against your own practice.
These tools produce estimates. Compaction, irregular geometry, breakage and local supply conventions all move the real number. Treat the output as a well-founded starting point, not a structural specification, and consult a licensed engineer for anything load-bearing.