How we estimate costs
The formulas, price sources and state adjustments behind every calculator.
Material quantities
Quantities use standard industry formulas: volume for concrete, gravel and mulch, surface area for paint, drywall, flooring, tile and roofing, and linear feet for fencing and railing. Each calculator page shows its exact formula. We add a waste allowance you can change, because real projects always need extra for cuts, spillage and mistakes.
Prices
National price ranges are compiled from current US retail listings for materials, published contractor cost guides, and industry pricing for labor. We show a low and high range rather than a single figure — the low end reflects basic materials and straightforward jobs, the high end reflects better materials, harder access and higher-cost contractors.
State adjustments
Construction costs differ widely by location. Each state has a relative cost index (1.00 = US average, ranging from about 0.84 to 1.32). Labor costs are scaled by the full index. Material costs are scaled by 40% of the difference, because materials vary less between regions than wages do. Mortgage estimates use each state's average effective property-tax rate.
What estimates don't include
- Permits, inspections and engineering, unless a calculator says so
- Hidden damage (rot, mold, structural repairs)
- Unusual access, very steep sites or remote locations
- Sales tax and delivery beyond typical local fees
Updates
Price data was last reviewed in September 2026. If you see a number that doesn't match your market, tell us.