Methodology

How we price your renovation

We would rather show you how a number is built than ask you to trust it. Here is what goes into every estimate, where it is weak and how you should use it.

Last updated: September 1, 2026

Every estimate is built line by line

Instead of multiplying your square footage by a single number, each calculator prices the individual parts of the job: materials, installed finishes, labor, demolition and disposal, permits, and a contingency buffer.

Each line has its own low and high unit price. The low total is the sum of the low prices and the high total is the sum of the high prices, so the range reflects real spread in the market. Changing one choice, such as cabinets or roofing material, reprices only the lines it affects.

Where the unit prices come from

Unit prices are national benchmark ranges for typical installed costs, rounded to planning-grade low and high values based on publicly reported cost guides and industry pricing. They are approximations. They are not a live feed of contractor bids and they are not quotes.

Every price range in the calculators is stored in one place per project and stamped with a review date. The current review date is shown on each calculator and in the table below.

How your state changes the number

Labor rates differ far more by location than material prices do. We apply a state cost index (US average = 1.00) to each line, weighted by how labor-heavy that line is. Materials move only a quarter as much as labor.

The state index is a planning approximation based on public wage and location-factor benchmarks. It does not capture differences between cities, or rural versus metro pricing inside a state.

Contingency and surprises

Renovations uncover surprises: rot behind a wall, an outdated panel, a slab that is out of level. We add a contingency line to every estimate. It is smaller for simple, contained jobs like windows and larger for projects that tie into the existing structure, like basements and additions.

What the estimates leave out

Estimates do not include design or architect fees unless a calculator says so, structural changes, hazardous material remediation (such as asbestos or mold), financing costs, furniture, or unusual site conditions. Each calculator page lists what is included and what is not.

Treat every result as a planning range for setting a budget and checking bids. Get at least three itemized written quotes from licensed contractors before you commit.

How fresh the prices are

Every calculator shows the month its unit prices were last reviewed, so you can judge how current a number is. Costs can move between reviews, for example lumber, metal roofing or copper wiring, so the ranges can lag behind the market. That is another reason to treat results as a range and not a price.

Calculator reference

Default estimates at national-average pricing, for the starting options in each calculator. Prices last reviewed September 2026.

Calculator	Default range	Line items	Contingency
Kitchen remodel	$24,000 – $48,900	11	8–15%
Bathroom remodel	$12,300 – $23,200	12	8–14%
Walk-in shower	$6,500 – $13,200	10	8–15%
Basement finishing	$33,300 – $66,000	8	10–20%
Flooring	$4,000 – $7,800	8	5–12%
Home addition	$73,000 – $154,800	9	10–20%
Garage conversion	$26,100 – $57,000	9	8–18%
Roof replacement	$10,000 – $21,400	7	6–15%
Siding	$15,100 – $30,300	7	6–15%
Windows	$5,800 – $10,700	7	5–12%
HVAC	$7,400 – $13,400	11	5–12%
Deck	$10,200 – $20,100	6	6–15%
Patio	$5,500 – $11,700	10	6–15%
Pergola	$5,900 – $12,600	8	6–15%

Independence

Some pages may include contractor matching or affiliate links. They never change the numbers in a calculator. See our affiliate disclosure for details.