About BuildCalc

How we calculate

Every material is sold a particular way, so we don't use a one-size-fits-all formula. Instead, each calculator uses the method that matches how its material is actually bought:

• By volume (mulch, topsoil, sand, gravel, concrete): quantity = area × depth, reported in cubic yards, plus bags and weight where relevant.
• By weight (asphalt): quantity = area × thickness × density, reported in US tons (and tonnes).
• By area or piece (flooring, pavers): quantity = area × (1 + waste), reported as square footage and the number of boxes or pavers needed.

All inputs are normalized to a single imperial base unit before any math runs, then converted back for display. That means the imperial and metric versions of a calculator always agree — there is only one formula to get right, not two.

Where our numbers come from

Densities, coverage rates, default depths, bag sizes, and waste factors are based on common industry values and calibrated against the figures published by established references such as Inch Calculator. We use these so our results line up with what a contractor or supplier would expect.

Loose materials don't have a single "true" density — moisture, gradation, and compaction all move the number. Rather than hide that, we pick a sensible typical value and show the realistic range on each calculator page (for example, dry sand at roughly 2,600–3,000 lb per cubic yard). Each page lists the source we calibrated against so you can check our work.

Why you can trust the math

The formulas behind every calculator live in one shared, version-controlled module — the same code runs on every page and in our automated checks, so two calculators can never quietly disagree. Each formula is covered by a regression test that asserts the output against a known hand-calculated value; if a constant or formula ever changes, those tests have to pass before anything ships.

Estimates, not promises

BuildCalc gives estimates for planning. Real quantities depend on site conditions, the exact products your supplier stocks, and how material is installed. Always confirm quantities with your supplier or a qualified professional before you buy, and order a reasonable overage. See our Terms for details.

Get in touch

Spotted a number that looks off, or want a calculator we don't have yet? We'd genuinely like to hear it — email us at [email protected] or use our contact page.