Calculation Methodology
How calculations work
Each calculator implements a documented formula applied to your inputs. Internal math uses SI base units (meters, square meters, cubic meters) for consistency, then converts results to US customary units for display when appropriate.
Validation rejects missing, non-numeric, or non-positive values where physical quantities must be greater than zero.
Units
Length, area, and volume fields accept US customary (feet, inches, square feet, cubic yards) and metric (meters, centimeters, square meters, cubic meters) inputs. Conversions use fixed factors — for example, 1 inch = 25.4 mm and 1 cubic yard = 27 cubic feet.
Weight results (gravel tons) use US short tons (2,000 lb) unless noted otherwise.
Waste factors
Material calculators optionally add waste as a percentage on top of net quantity: adjusted = base × (1 + waste% ÷ 100). Default waste values reflect typical residential practice but should be increased for diagonal layouts, complex roofs, or brittle materials.
Apply waste once in your workflow — either in a dedicated waste calculator or within a material calculator, not both.
Rounding
Display values round to practical precision (often two decimal places for volumes, whole units for counts). Paint gallons round up to the nearest quarter gallon. Bag, tile, and sheet counts round up to whole units because partial purchases are not available at retail.
Intermediate values retain full precision before final rounding to minimize cumulative error.
Limitations
Presets (dumpster sizes, truck tiers, BTU rules of thumb) are approximations. Site conditions, product lines, and regulations vary.
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