Cleaning units calculator
Machines are sold on PSI because it is the bigger, more exciting number. Cleaning units — pressure multiplied by flow — is the honest comparison, and it routinely shows that the cheaper machine with more flow beats the dearer one with more pressure.
Cleaning units — two machines
Cleaning units
12,000 vs 16,000
Machine B is +33% on cleaning units
Cleaning units is PSI multiplied by GPM. It is the only single number that compares two machines honestly — but flow is what rinses debris away, so between two machines of equal CU, take the one with the higher GPM.
PSI & nozzle quick reference
- 0 degRed
- Spot jet. Etches most surfaces.4000 PSI
- 15 degYellow
- Stripping bare concrete.4000 PSI
- 25 degGreen
- General concrete and walkways.3500 PSI
- 40 degWhite
- Siding, wood, vehicles.1500 PSI
- ~65 degBlack
- Detergent draw, low pressure.500 PSI
Pressure loosens, flow removes
Think of the two numbers as two different jobs. Pressure breaks the bond between the dirt and the surface. Flow carries the loosened dirt away and keeps the working area rinsed so you can see what you have done. A high-pressure, low-flow machine loosens grime and then leaves you pushing it around; a higher-flow machine at the same cleaning units finishes the same slab faster and cleaner.
| Class | Typical PSI | Typical GPM | Cleaning units |
|---|---|---|---|
| Consumer electric | 1600-2000 | 1.2-1.4 | ~2,400 |
| Consumer gas | 2800-3200 | 2.3-2.5 | ~7,500 |
| Prosumer gas | 3200-3600 | 3.0-4.0 | ~13,000 |
| Contractor belt-drive | 3500-4000 | 4.0-5.5 | ~20,000 |
| Trailer / skid | 3500-4000 | 5.5-8.0 | ~28,000 |
Class bands are indicative shapes of the market, printed so the arithmetic has something to sit against. No brand, no model, no price — those move weekly and would be stale by the time you read this.
The number that decides the surface cleaner