Methodology

This page exists so you can judge how much weight to put on our numbers. Every calculator also lists its own sources at the bottom of the page.

How an estimate is built

Every estimate is a sum of named line items, and each line is one of four kinds:

• Labor — hours of work, times what that trade is paid in your state, times a contractor markup. The hours come from published estimating references, manufacturer instructions and contractors' published crew rates. The wages are U.S. Bureau of Labor Statistics data for the specific occupation.
• Materials — quantities times current prices from retailers, distributors and manufacturers, adjusted by your state's price level for goods.
• Fees — permits and engineering, taken from official city fee schedules and published professional fees. State pages use that state's own figures.
• Percentages — contingency and similar allowances, as a share of everything else.

We show every line rather than a single total, because the line items are what let you compare one contractor's bid against another's.

Where the ranges come from

The low, typical and high figures are not our arithmetic hedging. Labor uses the 25th percentile, median and 75th percentile wage for the trade in your state, and each line carries the real spread in hours and prices we found. Two qualified contractors bidding the identical job will not return the identical number, and the range is meant to show how far apart they typically land.

How we check the numbers

Before a calculator is published, we run it against prices that real contractors publish on their own websites for defined jobs, in several states, and record where it lands. Where it misses, we check our own derivation before touching the source data. Where the evidence can't support a job type, we leave that job type out rather than guess.

One kind of line is calibrated rather than built from parts: for foundation piers, the cost of hydraulic equipment and lifetime warranties isn't published anywhere, so that line is the difference between labor plus materials and what contractors in that state charge per pier. It is labelled as such wherever it appears.

State pages

A state page uses that state's wages for each trade, its price level for materials, and the permit fees of its largest city, and it describes permit rules and local conditions specific to that state. We only publish a state page where we have that data. Where we don't, there is no page — a page that differs from the national version by nothing but a place name is not worth anyone's time.

What these numbers are not

They are not quotes, and nobody is bound by them. They do not account for the condition of your particular house, which is usually the largest single unknown. They are a starting point for a conversation with a contractor and a way to recognise a bid that is far outside the normal range.

How often figures are updated

Wage data is refreshed each year when the Bureau of Labor Statistics publishes new estimates, state price levels when the Bureau of Economic Analysis does, and material prices and permit fees when we re-check each calculator. Each source shows the date its data was true.

Corrections

If a figure looks wrong for your market, tell us and say why — we would rather fix it. Contact details are on the contact page.

How we make money

Right now, we don't — there are no ads or paid links on the site. If that changes, it will be through display advertising or referral fees from contractor matching services, it will be disclosed here and in our privacy policy, and it will never change the estimates. We do not accept payment from contractors to alter figures.