Methodology

Every formula, waste factor, and price on this site, and where it comes from.

Quantity formulas

Material math uses standard industry conversions: concrete at 27 cu ft per cubic yard with manufacturer bag yields (0.60 cu ft per 80 lb bag); bulk materials (gravel, mulch) at square feet × depth ÷ 324 for cubic yards; paint at 350 sq ft per gallon per coat; drywall fasteners at one screw per square foot; decking at 2.09 linear feet of 5.5" board per square foot; fence posts at 8-foot spacing; insulation depth as target R-value ÷ R-per-inch; epoxy at 231 cubic inches per gallon. Waste allowances follow trade practice: 10% default, 15% for diagonal layouts, 20% for complex tile patterns, 5% for sod.

Cost data

Prices are 2026 national averages compiled from published cost guides and retailer surveys (HomeGuide, HomeAdvisor/Angi, and major supplier pricing), shown as low–high ranges because real quotes vary by grade and market. State pages multiply national figures by a relative construction cost index (an RSMeans-style composite of local labor and material factors). Indexes are approximations — two metros in the same state can differ meaningfully.

What these calculators are not

They're planning tools, not engineering or quotes. They don't replace structural sizing (joist spans, footing depths, local code), and they can't see your site conditions. Use them to buy the right amount of material and to recognize a fair quote when you get one.

Updates

Prices drift; formulas don't. We review cost figures quarterly and date-stamp every page with its last review. Spot something off? Email contact@projectmaterialcalculator.com.