Methodology
How WashQuoter Calculates a Quote and Sources Its Guides
Every number in the quote engine and every claim in the guides traces to a documented method. This page describes both.
1. The quote engine formula
The calculator on the home page and inside the contractor dashboard uses a square-foot method with service-type multipliers, a trip charge, and an optional regional adjustment. The core formula is:
Job price = (Surface square footage × Base rate per sq ft × Service multiplier) + Trip charge + Add-ons
Base rates by surface
Default square-foot rates in the calculator are seeded from published contractor price surveys and can be edited by any contractor in their dashboard. The defaults are conservative midpoints from HomeAdvisor, Angi, and Thumbtack service-cost pages, cross-checked against real quotes from PWNA-member contractor listings. Because pricing varies widely by market, contractors should adjust the defaults to their local labor cost and demand.
| Surface | Default range ($/sq ft) | Typical driver |
|---|---|---|
| Concrete driveway | $0.10 to $0.30 | Stain load, moss, oil |
| House siding (vinyl, low-rise) | $0.15 to $0.35 | Story count, algae, gutters |
| Deck (wood) | $0.30 to $1.25 | Wood species, stain removal |
| Roof (soft wash) | $0.20 to $0.60 | Pitch, height, moss/lichen load |
| Commercial flatwork | $0.08 to $0.25 | Volume, night work, insurance requirements |
Ranges cross-checked against contractor rate posts on the PWNA and UAMCC public forums plus vendor education pages (Kärcher Professional, Hotsy). See /sources for the specific pages.
Service-type multipliers
Roof cleaning, deck restoration, and rust removal require softer techniques, more chemistry, or slower work than flat concrete. The calculator applies a multiplier on top of the base rate:
| Service | Multiplier | Why |
|---|---|---|
| Concrete flatwork | 1.0x | Baseline |
| Vinyl or fiber-cement siding | 1.2x | Soft-wash chemistry, ladder work |
| Wood deck restoration | 2.0x to 3.5x | Sanding, brightening, sealing |
| Roof soft wash | 2.0x to 3.0x | Fall risk, chemistry cost, slow rinse |
| Rust or graffiti removal | 3.0x+ | Specialty chemicals, extra time |
Trip charge
The default trip charge is $75. This covers drive time, fuel, tank fill, and setup. Contractors can set this per job or per zone in their dashboard.
Regional adjustment
Contractors can apply a percentage adjustment to reflect their metro's labor cost. We seed a small default map (high-cost metros +15 to +25 percent, low-cost rural counties -10 to -15 percent) drawn from BLS Occupational Employment Statistics for SOC 37-2011 (Janitors and Cleaners) and 37-3011 (Landscaping and Groundskeeping) wages. Contractors override the default whenever their local market disagrees.
2. What the calculator does not do
- It does not check that a contractor is licensed or insured. That is the contractor's responsibility. Our licensing guide shows where to check.
- It does not compute sales tax. Rules vary by state and by whether the service is treated as taxable. Contractors must set their own tax rate on the quote screen.
- It does not check chemistry safety. Contractors are responsible for handling sodium hypochlorite and other cleaning agents according to the current SDS and OSHA 29 CFR 1910 requirements. See our SH safety guide.
- It does not guarantee the quote will win the job. Close rate depends on the contractor's local market, communication, and follow-up.
3. How we research the guides
Every claim in a WashQuoter guide clears one of the following bars:
- Federal or state regulation. Cited with the CFR section, statute number, or state code number. Examples: OSHA 29 CFR 1910.132 (PPE), IRS Publication 583 (Starting a Business).
- Federal statistical agency. Bureau of Labor Statistics OES data for wages, US Census NAICS code 561790 for industry counts, SBA data for small-business benchmarks.
- Manufacturer specification sheet or SDS. Kärcher, Landa, Hotsy, General Pump, Cat Pumps, Steel Eagle for equipment. Univar, Brenntag, Coyne for chemical SDS. We cite the specific product and page.
- Recognised trade association. PWNA (Power Washers of North America), UAMCC (United Association of Mobile Contract Cleaners), IWCA (International Window Cleaning Association). We link to the specific published resource, not the homepage.
- State licensing board publication. For example, California CSLB, Florida DBPR, Texas TDLR, North Carolina LBGC. We cite the board's own published requirement.
If a claim cannot clear one of these bars, it does not go in the guide. Contractor forum lore, vendor marketing copy, and other blog posts are not primary sources and do not count.
4. Known limits and uncertainty
- Pricing benchmarks are ranges, not guarantees. Real closing prices vary by neighborhood income, competitive intensity, and whether the contractor is quoting a repeat customer or a cold lead.
- Licensing changes. States occasionally amend contractor licensing statutes. We review our licensing guide quarterly. If you rely on it for a licensing decision, verify with the state board.
- Chemistry data. SDS documents are revised. We cite by product name and revision date. Always check the current SDS for the exact product you buy, not the one we cited.
- Insurance premiums. We cite typical premium ranges published by industry insurance brokers (for example, Insureon, Next, Progressive Commercial). Your quoted premium depends on payroll, claims history, coverage limits, and state. Get a live quote from a broker.
5. Data refresh cadence
All guides in this batch carry a Last reviewed date of 30 June 2026. Wage and industry data (BLS OES, NAICS) is refreshed when the federal agency publishes a new vintage, typically annually. Chemistry and equipment specifications are refreshed when the manufacturer or SDS publisher issues a revision. Licensing tables are reviewed quarterly.
6. What we won't claim
- We will not claim WashQuoter is endorsed by PWNA, UAMCC, IWCA, OSHA, EPA, or any regulator.
- We will not claim a specific chemical is safe or unsafe. We describe what the SDS and OSHA guidance say, and we point you to the current SDS.
- We will not claim a specific insurance policy limit is enough for your business. We describe the categories and typical limits, and we point you to a licensed broker.
- We will not claim a specific piece of equipment is best. We publish the manufacturer's own specifications and let you compare against your needs.
- We will not claim the WashQuoter calculator will produce the correct market price for your job. It produces a defensible starting price you can adjust before you send the quote.
Last reviewed 30 June 2026. See /sources for the deep-linked source list.