How we calculate

Every CalcWall calculator follows the same rules, so you know what the numbers mean.

Formulas and sources

We use standard geometry and published conversion factors. Where a material has its own rule of thumb (for example coverage per bag), we use the figure printed by major US manufacturers and say so on the page.

Units and conversions

All calculations run in feet internally. Exact factors: 1 foot = 12 inches, 1 yard = 3 feet, 1 inch = 2.54 cm, so 1 foot = 0.3048 m. One cubic yard is 27 cubic feet.

Rounding

Results are shown to two decimals. Counts of items you buy, such as bags or boards, are always rounded up, because you can’t buy part of a bag.

Checking

Before a calculator goes live, its results are compared with hand calculations and a second independent source. If you spot an error, please tell us and we will fix it quickly.

Limits

Results are estimates for planning. Real projects vary with compaction, cuts and waste, so confirm quantities with your supplier before ordering.