Calculation methodology
How GQ Calc handles units, product assumptions, waste, package rounding, examples, and corrections.
Short version: geometry creates a net quantity. One explicit allowance creates an order quantity. Whole packages are rounded up last. Product-specific density, yield, coverage, and packaging stay editable.
Calculation rules
- Internal calculations use consistent base units. US volume converts from ft³ to yd³ by dividing by 27; a US short ton is 2,000 lb.
- Metric and US inputs convert to the same internal quantity before the formula runs. Intermediate values are not rounded.
- Order quantity equals net quantity × (1 + waste percentage). Waste is never silently applied twice.
- Packages equal the ceiling of order quantity ÷ package yield. The result shows any excess caused by that final rounding.
- Manufacturer ranges remain ranges. An uncertain 65–85 ft² coverage does not become a false “exact” midpoint.
Product values
Material density, bag yield, area coverage, roll dimensions, pallet coverage, and pack counts can change by product, region, moisture, grading, and installation method. GQ Calc provides sourced examples where the research supports them, but the value printed on the product or supplied for the project controls the estimate.
We do not maintain a regional price or product database. That keeps the calculators useful without implying that an old package or coverage value is still current.
Control examples and testing
Every launched calculator includes a static control example. Automated tests cover the documented examples, zero and invalid boundaries, unit equivalence, monotonic waste behavior, and package rounding. Pattern-aware wallpaper tests include free, straight, and half-drop cases.
What these tools do not decide
These calculators estimate material quantity. They do not select structural dimensions, reinforcement, load capacity, frost depth, stair safety, code compliance, installation systems, or material suitability. Use current product instructions and qualified project guidance.
Sources and maintenance
Each tool names the source used for its method or example. A source for one product is not transferred to every similar material. Links may change; if a source becomes unavailable, the editable input remains visible while the reference is reviewed.
Corrections
Found a formula, source, copy, or accessibility problem? Email hello@gqcalc.com with the calculator URL, inputs, expected result, and the product label or source you used. Reports are reviewed as product corrections, not individual project consulting.