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Quick answer
Pressure washer nozzles have two numbers: the spray angle (the color) and the orifice size. On General Pump's chart, the size number equals the flow in gallons per minute at 4000 PSI. A size 4.0 flows 4.0 GPM at 4000 PSI. At lower pressure the same nozzle flows less, so you match the size to your washer's rated PSI and GPM.
Replacement nozzles with 1/4-inch quick connect:
Simpson 80145 5-Nozzle Set Simpson 80143 Turbo NozzleFlow by nozzle size (General Pump chart)
| Nozzle size | Orifice (in) | GPM at 2000 PSI | at 2500 PSI | at 3000 PSI | at 4000 PSI |
|---|---|---|---|---|---|
| 2.5 | 0.036 | 1.77 | 1.98 | 2.17 | 2.5 |
| 3.0 | 0.040 | — | 2.37 | 2.60 | 3.0 |
| 3.5 | 0.043 | — | 2.77 | 3.03 | 3.5 |
| 4.0 | 0.046 | 2.83 | 3.16 | 3.46 | 4.00 |
| 4.5 | — | — | 3.56 | 3.90 | 4.5 |
| 5.0 | — | — | 3.95 | 4.33 | 5.0 |
Values are copied from General Pump's 2021 nozzle chart. A dash means we didn't copy that cell; see the PDF for the full grid. General Pump lists the orifice diameter for reference only.
How to read it for your washer
- Find your washer's rating. The label or manual lists maximum PSI and GPM.
- Find the PSI column closest to your washer's rating.
- Go down the column to the GPM closest to your washer's GPM. That row is your nozzle size.
Example from the chart: a washer rated about 2.6 GPM at 3000 PSI lines up with a size 3.0 nozzle. One rated about 3.5 GPM at 3000 PSI lines up with a size 4.0.
Check the kit you're buying
Replacement kits print the size. Simpson's 80145 set, for example, is orifice size 3.0, rated up to 3600 PSI, with 1/4-inch quick-connect plugs. Compare that to your washer before you order.
How we work: the flow figures are General Pump's published chart. Kit specs come from Simpson's product page. We copied the numbers, we didn't measure them. Sources are listed below.
Questions people ask
What does the number on a pressure washer nozzle mean?
On General Pump's chart, the size number is the flow in gallons per minute at 4000 PSI. A size 4.0 flows 4.0 GPM at 4000 PSI.
What nozzle size do I need for 3000 PSI and 2.5 GPM?
On General Pump's chart, size 3.0 flows 2.60 GPM at 3000 PSI, which is the closest row.
What orifice size are Simpson's replacement nozzles?
Simpson lists its 80145 five-nozzle set as orifice size 3.0, rated up to 3600 PSI.
Sources
Last checked Oct 23, 2026. Pressure washer spray can cause injection injuries. Lock the trigger before changing tips and release the pressure before disconnecting anything, as Simpson's manual says.
