Cleaning Units Calculator (PSI × GPM)
Cleaning units are PSI multiplied by GPM. Enter the PSI and GPM from your washer's listing or manual, and optionally a second machine, to compare. Cleaning units are a rough comparison of output, not a measure of cleaning quality, and they don't tell you which tip, distance or detergent suits a surface.
Simpson's FAQ puts it simply: "Cleaning units is calculated by multiplying PSI and GPM." That makes it a handy way to put two washers on one scale, as long as you feed it figures on the same basis. Makers state pressure differently. Some give a maximum and a rated (working) figure, some measure at a given nozzle, and some just list a number. So the calculator asks you to say which basis each figure uses, and it warns you if the two machines don't match. It has no built-in "typical" values and no product list: it uses only what you type. For what PSI and GPM mean on their own, read PSI vs GPM.
The calculator needs JavaScript. By hand: multiply your washer's listed PSI by its listed GPM. Compare two machines only when both figures are max or both are rated, as each maker states them.
How to use it
- Enter Machine A's PSI and GPM, from the listing or manual. Both are required.
- Pick the basis for Machine A: max, rated or as listed.
- Optionally, add Machine B's PSI, GPM and basis to compare.
You'll see cleaning units for each machine with the arithmetic shown. If both machines share a basis, you also see how they compare as a ratio. If they don't, you'll see: "These figures use different bases (max vs rated). Compare like with like."
Reading the result
Cleaning units are a rough comparison of output, not a measure of cleaning quality, and they don't tell you which tip, distance or detergent suits a surface. Use the lowest pressure that does the job.
Compare like with like: check whether both figures are max or rated, as each manufacturer states them.
Uses only the numbers you enter. Estimate / general guidance.
Without JavaScript
The formula is PSI × GPM = cleaning units. A worked example, with no particular machine in mind: 2,000 PSI × 1.2 GPM = 2,400 cleaning units.
See how to choose a pressure washer and all pressure washer picks.
FAQ
How do you calculate cleaning units?
Multiply PSI by GPM. Simpson's FAQ says: "Cleaning units is calculated by multiplying PSI and GPM." Use figures on the same basis, max with max or rated with rated.
Is a higher cleaning units number better?
Not on its own. A higher number means more output on paper, not a cleaner result, and it doesn't tell you which tip or distance suits a surface. Use the lowest pressure that does the job.
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