Calculator methodology

Last methodology review: 2026-07-25. Every result is a preliminary planning estimate, not a quote, engineered design, code determination, tax opinion, or lending offer.

Measurement model

Projects are reduced to standard geometry—rectangles, wall perimeters, triangular gables, sloped roof factors, depth-based volumes, or package coverage. Irregular projects should be divided into simple sections and totaled.

Package rounding

Bags, boxes, rolls, panels, sheets, bundles, and truck loads are rounded up because partial packages usually cannot be purchased. Some bulk products are rounded to common quarter-yard increments for planning; actual supplier minimums control.

Waste and allowances

Waste is applied only where the calculator identifies it. It may represent cuts, breakage, pattern matching, touch-up stock, compaction, settling, or grade variation. Users should replace the example percentage with a value appropriate for the product and layout.

Cost scenarios

The “typical” scenario uses entered prices, material tax, and labor-location factor. Budget and premium scenarios apply transparent multipliers around the same inputs. They are sensitivity ranges, not market-price claims or bids.

Default values

Defaults exist so a visitor can understand the tool immediately. They are examples, not current national prices. Product coverage, package size, labor, material prices, tax, incentives, utility rates, and financing terms should be replaced with verified project-specific information.

Quality control

Every calculator has automated tests for valid result structure and representative formula checks. Changes should update tests, review dates, examples, assumptions, and the sitemap together.