Pressure washer nozzle size calculator and chart
The colour on a tip tells you the spray angle. The number stamped beside it is the orifice size, and that is the part that has to match your machine. Enter the PSI and GPM from the data plate to get the size to buy, then check what a worn or wrong tip is really doing to your pressure.
Nozzle size from PSI and GPM
Pre-filled with a common contractor machine. Type your own data-plate figures.
Orifice size to buy
#4.5
Exact number 4.62; #4.5 builds 3,160 PSI on 4.00 GPM
The size number is the flow the tip passes at 4000 PSI. Spray angle does not change it, so pick the colour for the surface and this number for the machine.
| Stocked size | Pressure on your flow | Against your rating |
|---|---|---|
| #4.5 | 3,160 PSI | Above the plate |
| #5.0 | 2,560 PSI | Below the plate |
Check a tip you already have
Pressure this tip actually builds on your flow
3,160 PSI
105% of your rated 3,000 PSI
Matched. This tip builds within 10% of the pressure on your data plate.
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
What the size number on a tip means
Every pressure washer tip carries two things: a colour for the spray angle and a stamped number for the orifice. The number is a flow rating. A #4.0 tip passes 4.0 gallons a minute at 4000 PSI, a #5.5 passes 5.5, and so on. CAT Pumps, General Pump and Landa all publish their charts on that basis, and all three state that the spray angle does not change the flow. A green #4.5 and a white #4.5 behave the same on your machine.
flow = size × √(PSI ÷ 4000)
size = GPM × √(4000 ÷ PSI)
PSI = 4000 × (GPM ÷ size)²
The pump makes a fixed flow. The tip decides what pressure that flow is squeezed to on its way out. A tip that is too small asks for more pressure than the pump is built for; a tip that is too big lets the flow out at less pressure than you paid for. That is a different question from the one the pressure washer nozzle chart answers. The colour and angle are picked for the surface, using the surface PSI chart. The size number is picked for the machine, here, and once picked it stays the same across all five colours.
How to use this calculator
- Read the data plate. Enter the pump’s rated PSI and GPM. If the tap or tank cannot feed that flow, the real GPM is lower and so is the right size; the buffer tank size calculator covers the supply side.
- Count the tips sharing the flow. A wand has one. A two-arm surface cleaner splits the flow across two, so each tip is half the size. Pair this with the surface cleaner size calculator when you buy a disc.
- Buy the stocked size. Tips are sold in half-number steps. The table under the result shows the stocked sizes either side and what each builds on your flow.
- Check the tips you already own. Pick the stamped size and its condition to see the pressure it really makes, and whether it is matched, too small or too big.
Worked examples
Typical machine classes, run through the same formula. Flow sets the size far more than pressure does, which is the same lesson the pressure washer PSI guide and the cleaning units calculator teach from the other end.
| Machine | Plate | Exact | Buy | Builds |
|---|---|---|---|---|
| Homeowner gas | 3100 / 2.5 | 2.84 | #3.0 | 2,778 PSI |
| Prosumer gas | 3200 / 3.0 | 3.35 | #3.5 | 2,939 PSI |
| Pro residential, wand | 3000 / 4.0 | 4.62 | #4.5 | 3,160 PSI |
| Same machine, two-arm surface cleaner (2 tips) | 3000 / 4.0 | 2.31 | #2.5 | 2,560 PSI |
| Belt-drive | 4000 / 4.0 | 4.00 | #4.0 | 4,000 PSI |
| Skid unit | 3500 / 5.5 | 5.88 | #6.0 | 3,361 PSI |
| Trailer rig | 3500 / 8.0 | 8.55 | #8.5 | 3,543 PSI |
Plate is rated PSI / GPM. At small sizes a half step is a big jump: on the two-arm bar a #2.5 builds 2,560 PSI and a #2.0 would ask for 4,000. General Pump also lists #3.25 and #3.75 tips for exactly this gap.
Pressure washer nozzle size chart
Flow in GPM that each size passes at common working pressures. Find your machine’s flow in its pressure column and read the size on the left.
| Size | 2,000 PSI | 2,500 PSI | 3,000 PSI | 3,500 PSI | 4,000 PSI |
|---|---|---|---|---|---|
| #2.0 | 1.41 | 1.58 | 1.73 | 1.87 | 2.00 |
| #2.5 | 1.77 | 1.98 | 2.17 | 2.34 | 2.50 |
| #3.0 | 2.12 | 2.37 | 2.60 | 2.81 | 3.00 |
| #3.5 | 2.47 | 2.77 | 3.03 | 3.27 | 3.50 |
| #4.0 | 2.83 | 3.16 | 3.46 | 3.74 | 4.00 |
| #4.5 | 3.18 | 3.56 | 3.90 | 4.21 | 4.50 |
| #5.0 | 3.54 | 3.95 | 4.33 | 4.68 | 5.00 |
| #5.5 | 3.89 | 4.35 | 4.76 | 5.14 | 5.50 |
| #6.0 | 4.24 | 4.74 | 5.20 | 5.61 | 6.00 |
| #6.5 | 4.60 | 5.14 | 5.63 | 6.08 | 6.50 |
| #7.0 | 4.95 | 5.53 | 6.06 | 6.55 | 7.00 |
| #8.0 | 5.66 | 6.32 | 6.93 | 7.48 | 8.00 |
| #9.0 | 6.36 | 7.12 | 7.79 | 8.42 | 9.00 |
| #10.0 | 7.07 | 7.91 | 8.66 | 9.35 | 10.00 |
GPM, from flow = size × √(PSI ÷ 4000). These figures match General Pump’s and Landa’s published tables to two decimals; the 3000 PSI column is tinted because most residential work runs there.
A worn tip is a bigger tip
Water wears the orifice open. A worn #4.5 behaves like a #4.7 or a #5.0, and because pressure falls with the square of the size, a little wear costs a lot of pressure. Ten percent more flow through the hole means about 17% less pressure: 3,160 PSI new becomes 2,612 PSI. Nothing on the machine changed and nothing looks wrong. The spray just stops cutting.
Use the “Check a tip you already have” panel above with the condition set to worn to see your own numbers. The opposite mistake matters too. Landa’s chart puts it plainly: a tip that is too small can damage the equipment, and one that is too large costs cleaning ability.
Where the makers' charts differ
Injection injury risk
Questions people ask
Does a smaller nozzle increase pressure?
On the same flow, yes: a #4.0 on 4 GPM asks for 4,000 PSI. A 3000 PSI pump is not built for that: the unloader bypasses the difference, and makers warn an undersized tip can damage the equipment. If you need 4000 PSI, buy a pump rated for it; the 3000 vs 4000 PSI comparison covers what that buys.
Is the nozzle size the same as the colour?
No. The colour is the angle: red 0, yellow 15, green 25, white 40, black soap. The size number is the orifice. A set for one machine is five colours of the same size number.
What size nozzle for a 2.5 GPM, 3100 PSI homeowner machine?
A #3.0. The exact number is 2.84, and a #3.0 builds about 2,778 PSI on 2.5 GPM. If you are choosing between homeowner classes in the first place, read 2000 vs 3000 PSI.
Why does the soap tip have almost no pressure?
Because it is a huge orifice. General Pump and Landa both list their soap tip as a #40 at 65 degrees, and 4 GPM through a #40 works out to about 40 PSI. That pressure drop is what lets a downstream injector draw chemical; the downstream injector calculator takes it from there.
How often should tips be replaced?
No maker chart gives an hour count, and wear depends on hours and water quality. The test that works: fit a new tip of the same number. If the cleaning comes back, the old one had worn open. Tips are cheap next to the time a worn one wastes.