How we calculate
Every number on this site is produced the same way, from the same engine, and each page names its own sources. This explains the method and, more usefully, where it stops working.
One model per project
Each of the 36 calculators is a cost model: a base rate per unit, a set of project types that scale it, three finish levels, and a list of add-ons priced separately. Across the site that is 161 project types and 213 add-ons.
The estimate is the base rate multiplied by your size, your project type and your finish level, floored at the trade's realistic job minimum, then adjusted for your state, with add-ons stacked on top. Add-ons sit above the floor deliberately: a $6,000 extra on a job that hit a $2,000 minimum is still $6,000 of work.
The itemised breakdown is not decoration. The line items are shares of the same total, and they are forced to sum to exactly the figure shown above them, a breakdown that does not add up is where trust goes.
Where the rates come from
For each project we pull the live search results, read the cost ranges published by everyone ranking for it, and triangulate a rate that sits inside them. The sources and the capture date are printed on the calculator page itself, not buried here, so you can check them against the figure you were shown.
This is an honest description of a real limitation: these are published national ranges, not a licensed cost database and not observed bid data. Where our figure sits oddly against its own sources, that is a bug and we want to hear about it.
Regional adjustment
Labour is the part of a job that moves with geography. A crew in Boston costs more than a crew in Boise; a bundle of shingles does not.
So the adjustment is applied to labour only. We take the average weekly construction wage for your state from the BLS Quarterly Census of Employment and Wages, 2024 annual averages, NAICS 23 (Construction), private ownership, divide it by the national average of $1,559 a week, and apply the resulting index to 45% of the project cost. That covers all 51 states and DC.
We used the 2024 annual figures rather than 2025 on purpose: the 2025 file is still preliminary and suppresses private construction wages in more than twenty states. A complete year beats a fresher one with holes in it.
We chose a federal wage series over a construction cost index because the standard cost indices are paywalled, and the free tables circulating online are self-described order-of-magnitude estimates, several of them now openly AI-generated. Publishing those as researched figures would be worse than publishing nothing.
What these numbers cannot tell you
- Anything below state level. The gap between a metro and a rural county inside one state is often wider than the gap between states. Manhattan and upstate New York share a multiplier here and do not share a labour market.
- The condition of your house. The single biggest source of variance in real quotes is what a contractor finds once work starts, and no calculator can see it.
- Your local permit and code requirements. We carry a typical permit share, not your jurisdiction's fee schedule.
- What the market is doing this month. A busy season, a materials spike or a shortage of one trade moves prices more than any input on this site.
- Access and site conditions. Some of this is captured as add-ons, a sloping site, a difficult attic, but only roughly.
How to use an estimate well
Use it to size the problem and to sanity-check a quote. If a contractor's figure sits far outside the range here, that is not proof they are wrong, but it is a reasonable thing to ask them about, and the itemised breakdown gives you the vocabulary to ask.
Then get the quote in writing, from someone who has visited. That is the only number you can act on.
How this site makes money
If you choose to submit your details, we pass them to home improvement companies and are paid for the introduction. Using a calculator never requires it. The full estimate is shown before we ask for anything, and there is no account and no email gate.
We say this plainly because it is the obvious question about a free calculator, and because the answer affects how you should read the rest. What we do not do is inflate estimates to make enquiries look more urgent. The numbers are checked against their own sources on every build, and the FAQ figures on each page are verified against the live calculator so the copy cannot drift from the tool. See who receives an enquiry. We also use Google Analytics to see which calculators earn their place; what it collects and how to decline it.
Common questions
- Where do the cost ranges come from?
- Each calculator's rates are triangulated from the published ranges of the sources ranking for that project, captured on a stated date. Every calculator page lists its own sources and that date in the 'Why trust these numbers?' panel. They are not a single licensed dataset, and we do not claim they are.
- How is my location taken into account?
- Your ZIP code resolves to a state, and the labour portion of the estimate is scaled by average construction wages in that state, from BLS Quarterly Census of Employment and Wages, 2024 annual averages, NAICS 23 (Construction), private ownership. Materials are treated as national, because lumber and shingles cost much the same everywhere. Nothing else about your ZIP is used.
- Why is the regional adjustment smaller than the wage difference?
- Because only part of a bill is labour. A state paying 25% above the national construction wage does not make a project 25% dearer, since roughly 55% of what you pay is materials priced nationally. Passing the wage gap through whole would overstate what the data supports.
- How accurate are these estimates?
- They are directional. They are good enough to tell you whether a project is a $5,000 problem or a $50,000 one, and whether a quote you have been given is in a normal range. They are not good enough to budget from. Only a contractor who has seen the property can give you that.