Sources & data notes
How we calibrate the numbers behind each calculator, and why our estimates are ranges instead of single prices.
Why estimates are ranges
The same project can vary 30-100% depending on access, demolition required, regional labor rates, contractor backlog, season, material availability, and code requirements that change by jurisdiction. A single price would be wrong almost every time. A range, paired with the actual cost drivers shown as line items, gives you something you can act on.
Each calculator's range is wide enough to cover the realistic spread of project conditions, and narrow enough that the midpoint is a useful starting point for budgeting.
Source families
Published rate rows draw on public benchmarks, government wage and price data, supplier pricing, and clearly-labeled internal assumptions. Below is what each family covers and how we use it — followed by how heavily we actually lean on each one, counted from the files rather than asserted.
Concentration, counted from the published rate files rather than described from memory. There are 1,233 rate rows across the 55 calculators, and they are not evenly sourced:
| Source | Family | Rows | Share | Calculators |
|---|---|---|---|---|
| homeguide.com | cost guide | 698 | 56.6% | 47 |
| (internal assumption) | internal | 144 | 11.7% | 30 |
| homewyse.com | cost guide | 86 | 7.0% | 21 |
| data.bls.gov | official | 63 | 5.1% | 50 |
| homedepot.com | supplier or manufacturer | 53 | 4.3% | 13 |
| homeadvisor.com | cost guide | 25 | 2.0% | 11 |
| angi.com | cost guide | 24 | 1.9% | 8 |
| codes.iccsafe.org | official | 11 | 0.9% | 8 |
Read that honestly: 69.3% of rows cite a public cost guide, and homeguide.com and homewyse.com alone account for 63.6%. Government and standards sources account for 10.3%. That concentration is a real limitation of these estimates, not a detail: where several guides disagree about a trade, our range inherits whichever one we read. Diversifying the highest-traffic and highest-cost trades is ongoing work, and this table is generated from the files themselves so it cannot drift away from what we actually cite.
Public cost guides
HomeGuide, Homewyse, HomeAdvisor and Angi, with a few rows from LawnStarter, ConcreteNetwork, SolarReviews, EnergySage and FenceAdvisors. They give national-average installed and material ranges. HomeGuide is by far the most cited (see the counts above), and on about a third of the calculators it is the only cost guide cited, so those estimates carry its view of the market.
Government labor + price data
We use Bureau of Labor Statistics Occupational Employment and Wage Statistics (OEWS) as a wage benchmark by trade. ProjectCostPro does not treat BLS wages as contractor prices directly; we model loaded crew billing rates by adding payroll burden, overhead, equipment, supervision, and contractor margin assumptions on top of the wage data. BLS Producer Price Index series are used as a broad signal for material-cost movement, not as a direct local price quote. IRS Form 5695 and 8911 inform federal energy / EV credit guidance; EPA standards inform radon, mold, and lead-paint scope.
Building code references
We use International Code Council model codes, trade standards, and common AHJ practices to structure scope items such as permits, inspections, venting, clearances, egress, energy requirements, and safety-related exclusions. Local code adoption varies by city, county, and state — many jurisdictions are on older model-code editions or have local amendments — so these references guide calculator logic but do not replace local permit review.
Manufacturer / supplier benchmarks
We use published MSRP, retail listings, and supplier-visible pricing snapshots from manufacturers and major retailers (Home Depot, Menards, United Rentals, Mitsubishi Electric, Schluter, Trex, RadonAway, Bona, Morton Buildings, James Hardie, Rockwool, Aprilaire, Custom Building Products, and others) as material-cost benchmarks. These are not live quotes and may differ from local contractor pricing, distributor discounts, freight, minimum orders, and seasonal availability.
Industry standards
IICRC S520 for mold remediation containment levels. NRPP for radon mitigation. NWFA for hardwood refinishing. ICC for permit treatment. These define scope structure, not price — we use them to make sure our line items match the work that actually gets done.
Cost-book calibration
We use published estimating references only as internal calibration tools for unit logic, crew-hour sanity checks, and range reasonableness. We do not copy, republish, or expose protected tables, prices, descriptions, or formulas. Public site data is independently modeled from public sources, supplier benchmarks, and ProjectCostPro assumptions.
Internal assumptions
Where public data is thin — mobilization minimums, emergency call-out fees, access difficulty, regional friction, small-job premiums — we use internal assumptions calibrated against multiple public guides and supplier-visible pricing snapshots. Internal rows come in two kinds, each labeled in the rate file: internal-assumption for planning logic such as minimums and access factors, and internal-baseline for a price not yet matched to a public source, often because the page it cited went dead. Both are counted in each calculator’s source note and should be read as planning logic, not source-quoted prices.
How we update rates
Rate tables are designed to carry source_url, source_date, and lastUpdated fields where applicable, so published rate rows can be audited and reviewed over time. Our target is to review high-impact rates regularly, refresh outdated source links, and re-check regional spread when material or labor markets move. If you spot a number that appears clearly wrong, tell us — we use that feedback to cross-check the relevant calculator and source assumptions.
What ZIP-zone pricing actually is
The ZIP / state input on each calculator applies a planning-zone adjustment to material, labor, and equipment costs — not exact local supplier or bid pricing. We use a curated set of metro zones plus state averages for the rest of the country, calibrated against published regional cost spreads. Two ZIPs in the same metro will return the same multiplier; real contractor pricing within a metro can still vary based on neighborhood, supplier proximity, and crew availability.
These methods make the estimates more useful for planning, but they do not replace a site visit, local code review, or a written contractor bid.
Why local quotes will differ
- Real site conditions (rock, water table, access, parking)
- Local contractor backlog and seasonality
- Code requirements specific to your AHJ (energy, hurricane, seismic, snow load)
- Material availability and freight
- Whether your project is bundled with neighboring work
- Demolition, abatement, or rework not visible until walls are open
Use ProjectCostPro for planning. Always get 2-3 written bids from licensed contractors before signing.
Editorial, source, and correction policies
Editorial policy
Each calculator is built around the actual scope decisions for that trade — material grade, dimensions, access difficulty, demolition, and permits — rather than a single national-average number. Calculator structure, scope language, and assumptions are reviewed against published cost guides, manufacturer documentation, code references, and industry standards before any rate row is added or changed.
Source policy
We prefer primary sources where they exist: government data (BLS, EPA, DOE, ENERGY STAR), code and standards bodies (ICC, IICRC, NRPP, NWFA), manufacturer pricing pages and major retailer listings. In practice public cost guides carry most of the data: HomeGuide alone is cited on more than half of all rate rows, and for many line items it is the only source. Cost-engineering reference books are used only for internal calibration and unit-logic sanity checks; we never copy or republish protected tables, prices, or formulas. Where public data is thin, internal assumptions are clearly labeled in the rate tables and treated as planning logic, not source-quoted prices.
Correction policy
If a published number looks clearly wrong, tell us — include the calculator name, the inputs you used, and what you got quoted locally. We re-check the source row, update the underlying CSV if warranted, and refresh the lastUpdated date so the change is auditable. We aim to acknowledge feedback within a few business days; resolution time depends on whether the change is a single-number tweak or a structural revision to the calculator.