- Tested math. Every calculation engine ships with an automated test suite pinned to hand-verified values. The formula behind each tool is printed on its page.
- Cited sources. Material factors (bag yields, densities, coverage rates) come from manufacturer specifications; code references name the section (e.g. IRC R506.1). If we can't source a number, we don't publish it.
- Honest rounding. Quantities round the way suppliers sell — up, never down — and waste allowances are visible and editable, never hidden in the result.
- Dated updates. Each calculator shows when it was last reviewed. Price defaults are revisited as markets move; your local quote always beats our default.
- Estimates, not engineering. These tools size orders. They are not a substitute for a structural engineer, an inspector, or your local code.
Editorial standards
What "checked" means on a TrowlCalc page.