Methodology

What we do (and what we don't)

Our calculators are planning tools. They convert your measurements into a practical material estimate using common formulas and reasonable assumptions.

They are not a substitute for local code, manufacturer specifications, or a professional takeoff for critical projects.

Units and conversions

• We keep formulas consistent: area x thickness = volume, and we convert units before multiplying.
• When suppliers sell in different units (yards vs tons, boxes vs sq ft), we provide a planning conversion and recommend confirming your exact product label or supplier conversion.
• If your project mixes footprint and slope dimensions (roofing) or varies in thickness (sloped beds), use average thickness and measure more than one point.

Rounding and minimums

• Many materials are purchased in whole units (sheets, bags, boxes, bundles). We round up because partial units aren't practical to buy.
• Running short mid-project often costs more than a small buffer (extra trips, mismatched dye lots, cold joints).
• If your supplier has minimum delivery charges or minimum load sizes, round to the nearest sensible order size.

Waste (overage) factors

Waste is not just mistakes. It includes cuts, offcuts you can't reuse, breakage, mixing loss, uneven subgrade, and rounding to whole purchase units.

• Simple rectangular projects usually waste less than complex shapes and patterns.
• Diagonal layouts, many corners, and many penetrations typically increase waste.
• If matching later is difficult (tile dye lots, paint batches), buying enough up front is usually safer.

Assumptions and sources

We use common industry formulas (area/volume conversions, packaging conventions like roofing squares, and typical coverage ranges).

For best accuracy, always prefer the exact product label coverage, manufacturer installation requirements, and your supplier's conversions for the specific material you're buying.

If you find an assumption that doesn't match your region or product, contact us and include the product and context. We continuously improve the calculators.