Methodology.
Exactly how every estimate on this site is calculated, where the numbers come from, and what they don't capture.
The short version
Every calculator on this site runs the same formula against a small set of configured numbers: a baseline material/labor cost per project type, a multiplier for the material tier and labor complexity you select, and a multiplier for your state or country. Nothing on this page is a live data feed — it's a static, transparently-documented set of assumptions that we review and update periodically, not a real-time pull from contractor databases.
The formula
Every estimate is calculated as:
This runs three times per calculation — once each against the configured Low, Average, and High base rate — to produce the three-tier range shown in every calculator. This is the exact function used by the live calculators (src/utils/calculator.ts in the site's source), not a simplified description of it.
Worked example
A 2,000 sq ft roof replacement, standard material tier, standard labor complexity, national average (no state adjustment):
Hypothetical example for illustration only — not a claim about what any specific real roof costs. Use the live calculator for a number based on your actual project.
Where the base rates come from
Each of the 10 calculators has a configured baseline Low / Average / High cost per unit (per square foot, linear foot, window, or flat project) and a labor-share percentage. These are set from publicly available industry cost-range information — the kind of figures published by trade associations, government labor statistics, and general contractor cost guides — condensed into a single baseline per project type. They are not the output of a proprietary contractor survey, a live pricing API, or a panel of reviewing tradespeople; we don't claim otherwise anywhere on this site.
The current baseline figures were last reviewed for 2026. We intend to revisit them periodically as general construction cost trends shift, and will update this page's "last reviewed" note whenever we do.
Base rates and labor share, as currently configured, by project type:
| Project | Base Rate (Low–High) | Unit | Labor Share |
|---|---|---|---|
| Roof Cost Calculator | $4.50–$12.00 | sq ft | 60% |
| Deck Cost Calculator | $22.00–$65.00 | sq ft | 50% |
| Fence Cost Calculator | $15.00–$50.00 | linear ft | 45% |
| Flooring Cost Calculator | $4.00–$18.00 | sq ft | 40% |
| Bathroom Remodel Calculator | $6500.00–$28000.00 | flat project | 55% |
| Kitchen Remodel Calculator | $12000.00–$55000.00 | flat project | 45% |
| HVAC Replacement Calculator | $4800.00–$15000.00 | system | 40% |
| Window Replacement Calculator | $450.00–$1600.00 | window | 35% |
| Siding Cost Calculator | $5.50–$20.00 | sq ft | 50% |
| Driveway Cost Calculator | $5.00–$18.00 | sq ft | 50% |
Regional multipliers
Every US state (plus regions in Canada, the UK, Australia, India, Germany, South Korea, Hong Kong, Brazil, and France) has a configured labor multiplier and material multiplier, expressed relative to a 1.0x national baseline. These reflect general, directionally-reasonable regional cost differences — states widely understood to have a higher cost of living and stricter licensing/insurance costs (e.g. California, New York, Hawaii, Massachusetts) carry higher labor multipliers; states with a lower cost of living carry lower ones. They are configured estimates set by the site owner, not the output of a per-state contractor wage census, and shouldn't be read as that precise.
Currency conversion
For calculators used outside the United States, displayed figures are converted from the USD base calculation using a fixed exchange rate configured in the site's data files — not a live foreign-exchange feed. These rates are approximate and are only refreshed when the site's data is manually reviewed, so they can drift from the real-time rate between updates. Non-US estimates should be treated as directional, not precise.
What isn't in the model
- Permit and inspection fees (vary too much by municipality to estimate reliably)
- Demolition/disposal beyond standard tear-out for the project type
- Structural repairs or code-driven upgrades discovered once work starts
- Design fees, financing costs, and sales tax
- Real-time material price volatility (tariffs, supply shocks, seasonal demand spikes)
We suggest budgeting an additional 5–15% on top of any estimate to cover these — the exact figure depends heavily on your project and municipality.
Limitations
This is a formula, not a site visit. It has no information about your property's actual condition, access, existing damage, or local permitting quirks — all of which move a real contractor's bid. Use these estimates to sanity-check bids and plan a rough budget, not as a number to hold a contractor to. See our FAQ for how to compare a real quote against this range.
Corrections
If you spot a base rate, multiplier, or formula that looks wrong, tell us — see our Contact page. Details on how we handle correction requests are in our Editorial Policy.