1. Base prices come from cross-referenced public data
For each project we collect installed-cost figures from several established public sources — including Homewyse, HomeGuide, Fixr, and retail pricing from Lowe's and Home Depot — and take a sensible range across them rather than trusting any single number. National cost guides disagree with each other all the time; the honest answer is a band, not a point. Every calculator lists the specific sources behind its numbers at the bottom of the page.
2. We split materials from labor
Each installed price is divided into a materials share and a labor share based on typical ratios for that trade. This is what lets the tools show a do-it-yourself estimate (materials, plus a small allowance for hardware and tool rental) next to a hire-a-pro estimate, and show you what the labor is actually worth.
3. We adjust for your state
The same project costs very different amounts in different places, mostly because construction labor wages and regional material and permit costs vary. We apply a state cost index where 1.00 is the U.S. national average. These coefficients are planning-grade: they are seeded from public regional cost data and are being recalibrated against U.S. Bureau of Labor Statistics construction-trade wages by state. The state-by-state table on each calculator is generated directly from this index.
4. We publish ranges, not promises
Every result is a range. Your actual cost depends on things no calculator can see: site access and slope, soil and drainage, demolition of what's already there, design complexity, permit fees, the season, and how busy local contractors are. Use our numbers to set a budget and sanity-check bids — then get firm quotes from licensed local pros before you commit.
5. We date everything and update quarterly
Prices move. Each calculator and the state index carry a "last updated" date, and we revise the underlying data on a quarterly cadence so the figures track current conditions. If a number looks stale, check that date — and tell us, because we'd rather fix it than defend it.
In plain terms: these are well-researched planning estimates, not appraisals or quotes. We make no guarantee that any project will fall within a stated range. Current price data vintage: June 2026.