Methodology · Last updated September 2026
How HomeEstimatorHub calculates an estimate
The exact model behind every calculator on this site — the formula, the regional multipliers, where the numbers come from, and what they cannot tell you.
The short version
Every calculator here works the same way. It starts from a base rate for the type of work, scales it by the things that actually drive cost on that job, adds any fixed-price extras you select, and then applies a regional multiplier for your state and area type. The result is shown as a single figure and a range.
No estimate on this site is generated on demand by a language model, and none of it is a quote. It is arithmetic over a rate table that is maintained by hand.
The formula
subtotal = base_rate × scope_multipliers
total = (subtotal + fixed_addons) × state_multiplier × area_multiplier
low = total × range_low
high = total × range_high
- Base rate — a starting figure for the configuration you picked. On the radon calculator, for example, a basement or slab-on-grade system starts at $1,200 and a block wall foundation at $2,200, because block wall systems need more suction points and sealing.
- Scope multipliers — the variables that genuinely move the price: square footage, severity, material grade, height, thickness. These scale the base rate rather than replacing it.
- Fixed add-ons — discrete options priced as flat amounts and added before the regional adjustment, because a $500 extra suction point costs more to install in New York than in Mississippi too.
- Regional multipliers — your state, then how built-up your area is. Both are applied last, to the whole job.
A worked example
A 2,000 sq ft home with a basement, a radon reading of 8 pCi/L, in suburban Ohio, with no extras:
size factor (2,000 sq ft) = 1 + 0.15 × (2000 − 1500) / 1000 = 1.075
level factor (8 pCi/L) = 1 + 0.05 × (8 − 4) = 1.20
────────────────────────────────────────────────
subtotal = 1200 × 1.075 × 1.20 = $1,548
Ohio multiplier = 1.05
suburban multiplier = 1.00
────────────────────────────────────────────────
estimate = $1,625 (range $1,219 – $2,194)
You can reproduce this on the radon mitigation calculator. Every tool shows its own breakdown in the results panel.
Where the base rates come from
Base rates are maintained by hand by Kapil Lodhi. They are compiled from published contractor and supplier pricing, manufacturer list prices, and industry cost guidance for each trade, then adjusted as reader corrections come in.
Being straight about the limits. These rates are not drawn from a licensed commercial construction-cost database, and they are not independently audited. They are a researched starting point, not a survey of what your local contractors charge this week.
Work is underway to rebuild the labor component of every calculator on BLS Occupational Employment and Wage Statistics — state-level mean hourly wages for the specific trades each tool models. When that lands, this page will show the wage figures and the occupation codes behind each one.
Regional multipliers
Twenty-eight of the calculators on this site ask for your state. All of them use the same table, applied to the whole job after scope. The national baseline is 1.00; the table runs from 0.88 (Mississippi) to 1.28 (New York).
| State | Multiplier |
|---|---|
| Alabama | 1.00 |
| Alaska | 1.10 |
| Arizona | 1.05 |
| Arkansas | 0.92 |
| California | 1.25 |
| Colorado | 1.08 |
| Connecticut | 1.18 |
| Delaware | 1.05 |
| Florida | 1.00 |
| Georgia | 0.95 |
| Hawaii | 1.12 |
| Idaho | 0.93 |
| Illinois | 1.10 |
| Indiana | 0.97 |
| Iowa | 0.91 |
| Kansas | 0.90 |
| Kentucky | 0.93 |
| Louisiana | 0.92 |
| Maine | 1.05 |
| Maryland | 1.15 |
| Massachusetts | 1.20 |
| Michigan | 1.08 |
| Minnesota | 1.02 |
| Mississippi | 0.88 |
| Missouri | 0.95 |
| Montana | 0.92 |
| Nebraska | 0.91 |
| Nevada | 1.05 |
| New Hampshire | 1.12 |
| New Jersey | 1.22 |
| New Mexico | 1.00 |
| New York | 1.28 |
| North Carolina | 0.95 |
| North Dakota | 0.90 |
| Ohio | 1.05 |
| Oklahoma | 0.91 |
| Oregon | 1.08 |
| Pennsylvania | 1.18 |
| Rhode Island | 1.15 |
| South Carolina | 0.95 |
| South Dakota | 0.90 |
| Tennessee | 0.93 |
| Texas | 0.98 |
| Utah | 1.00 |
| Vermont | 1.10 |
| Virginia | 1.12 |
| Washington | 1.15 |
| West Virginia | 0.95 |
| Wisconsin | 1.05 |
| Wyoming | 0.92 |
Area type
Applied on top of the state figure, because labor inside a metro runs well above the same state's rural rate:
| Area | Multiplier |
|---|---|
| Rural | 0.88 |
| Suburban | 1.00 |
| Metro | 1.18 |
State and area are the only geographic inputs today. That is coarser than it should be — costs inside a single state vary by metro, and moving to a finer geography is the next planned change.
What the range means
Every calculator shows a low and a high alongside the headline number. That band is not a confidence interval in the statistical sense — it reflects how much the price of that particular kind of work is known to swing once a real contractor sees the site.
The band width is set per calculator, and it is deliberately not uniform. Tightly specified work such as driveway sealcoating carries a narrow band of roughly −15% to +18%. Open-ended work where site conditions dominate — foundation repair, sewer line replacement — carries a band as wide as −35% to +75%.
If your quotes land inside the band, the estimate did its job. If every quote lands outside it, the base rate for your area is probably wrong, and I would genuinely like to hear about it.
Accuracy
There is no validated accuracy figure for these tools, and this page will not invent one.
An earlier version of the About page said estimates were “typically within 15–25% of actual contractor quotes.” That claim was never measured against collected quotes, so it has been withdrawn rather than restated here.
Publishing a real accuracy figure requires a body of actual quotes to compare against. Collecting those is in progress — see below. When there are enough submissions in a category to say something honest about it, the measured spread for that category will be published on this page, with the sample size next to it.
How often this is updated
- Rate tables — reviewed on a rolling basis across the year; the “last updated” date on each calculator reflects the last time that specific tool was revised.
- Regional multipliers — reviewed annually, and whenever the underlying wage data is refreshed.
- Code and standards references — checked when the referencing body publishes a new edition.
- Reader corrections — applied as they arrive and are verified.
Dates shown on this site are the real dates the content was last changed. Nothing here is post-dated or scheduled ahead.
What these tools are not
- Not a quote. No contractor is bound by anything here. Get at least three written bids.
- Not professional advice. I am not a licensed contractor, engineer, inspector or financial adviser. For anything structural, electrical, or involving asbestos, radon or mold, the relevant licensed professional decides — not a calculator.
- Not a lead generator. Nothing on this site sells your details. The calculators run entirely in your browser and your inputs are never sent anywhere.
- Not a substitute for your local building department. Permit requirements and code amendments are local and they change.
Help make the numbers better
The single most useful thing anyone can send is a real number: what you were actually quoted or actually paid, for what scope, in what state. Corrections from people who have paid the bill are the fastest way this improves — and they are what will eventually make a published accuracy figure possible.
Email kapil@kapilseo.com, or use the contact form. If a figure on this site is wrong, say so plainly and it gets fixed.
Sources & standards
Reference data and standards this methodology draws on or plans to draw on.