The Cost Desk

Methods

How we build the numbers

Every estimate here is arithmetic you can follow: what the work takes, what the parts cost, and what a contractor has to charge to stay in business. This page shows the formula and the data.

The formula

The same five lines for every project. Each one gets a low value and a high value.

  1. Labor. Hours the job takes, times what the trade is paid an hour, plus what the employer pays on top for payroll taxes, insurance and benefits.
  2. Materials. Shelf prices for the parts, plus extra for waste and offcuts.
  3. Permits and inspections. A fee per job. Towns differ, and some charge nothing.
  4. Haul-away. Taking the old material away.
  5. Overhead and profit. Added on top of the other four: the office, vehicles, insurance, advertising and the owner's profit.

A worked example

Roof replacement (asphalt shingles), 2,000 sq ft of roof, US average. This table is generated from the same data as the project page, so it cannot drift out of date.

Worked example for Roof replacement (asphalt shingles)
LineHow it is worked outLowHigh
Labor2,000 sq ft x 0.02–0.04 hours per sq ft x $22.24–$31.44 an hour x (1 + 23–30% payroll costs)$1,094$3,270
Materials2,000 sq ft x $1.65–$2.14 x (1 + 12% waste)$3,696$4,794
Permits and inspections$100–$300 per job$100$300
Haul-away and disposal2,000 sq ft x $0.15–$0.40$300$800
Overhead and profit40–60% on top of the four lines above$2,076$5,498
Planning range$7,266$14,661

The low column uses every low input and the high column every high input, so the range is deliberately wide. $3.63 to $7.33 per sq ft.

How sure are we?

Every assumption on a project page carries one of three labels.

Checked source
We read the figure ourselves on the source's own page or table, and recorded the date.
Published, secondhand
A published figure we could not check at the source: a trade article, a study summary, a number reposted by another site.
Our estimate
Our own judgment where we found no source. We say so, and we replace it when a source turns up.

If you know better, you can say so. Open Fine-tune the estimate on a project page and move the sliders for how long the work takes or what the materials cost. The estimate follows, and your numbers stay in your browser and in the link you copy.

What these numbers are not

  • They are not quotes. A contractor prices your actual roof, your town and the week they are busy.
  • Wages are what employers pay workers, taken from federal statistics. They are not what a contractor charges.
  • The state adjustments are rough. Materials and permit factors use state consumer price levels as a stand-in, because no direct source exists.
  • The overhead and profit range comes from US Census averages for whole industries, including new construction and commercial work.
  • Surprises are not included: rotted wood under a roof, a corroded pipe, code upgrades, asbestos.
  • Nothing here is medical, legal, tax or financial advice.

Where the data comes from

All sources used by the projects on this site, with the year the data describes and the date we last checked.

Keeping it current

  • Shelf prices are re-read at least twice a year and the date is shown next to them.
  • Wage, price-parity and Census data are updated when the agencies publish new editions.
  • Every project page gets a full re-check at least once a year, and sooner when a wage release, a tax rule or a shelf price moves sharply. A page changed that way is listed in the correction log.
  • If you find a mistake, tell us. We publish every correction.