How we estimate project costs

Each of the 40 project categories has a hand-maintained national range — low, typical and high — priced per square foot, per linear foot, per unit or per job, whichever matches how contractors actually bid that trade. Roofing is priced per square (100 sq ft); windows per window; plumbing per job.

Individual project types adjust that baseline. A metal roof is not an asphalt roof, so it carries a multiplier rather than sharing a number that would be wrong for both.

This is the part that makes a local estimate mean something. Materials are largely national commodities that differ by freight and regional demand. Labour is not — a crew day rate varies enormously between markets.

So each project carries a labour share, and the local index is applied in full to that share and at 40% strength to the materials share. Interior painting is about 75% labour and swings a long way between markets. A solar install is about 30% labour and barely moves. Applying one flat multiplier to everything would overstate the local difference on equipment-heavy jobs and understate it on labour-heavy ones.

The index combines two things: a state-level construction cost index reflecting prevailing trade rates and regional materials pricing, and a metro-size adjustment, because larger markets carry higher overhead, permit costs and trade demand.

On our current state index, the least expensive markets are Mississippi, Arkansas, Alabama, Oklahoma, South Carolina; the most expensive are Hawaii, Alaska, New York, California, Massachusetts.

Estimates are rounded to a precision the model can actually support. A range of “$18,472 to $31,208” would imply an accuracy no cost model has and no contractor would quote to, so you will see $18,500 to $31,000 instead.

These figures are not quotes, bids or offers. No contractor has agreed to any price shown here. Real bids are shaped by things a model cannot see: the condition of what is behind your walls, your local permit office, how busy the trade is this month, and how you and the contractor get on.

Use these numbers to sanity-check a bid, to budget before you call anyone, and to know when a quote is worth a second opinion. Then get written bids from licensed local professionals.

If a figure looks wrong for your market, it may well be — this model is maintained by hand and improves with correction. Get in touch and tell us the project, the city and what you were actually quoted.