Choosing the wrong nozzle size is one of the fastest ways to lose pressure, damage equipment, or just waste time on the job. It's not complicated but a lot of people guess. Guessing is what causes problems.
The Two Numbers That Matter: PSI and GPM
Every pressure washer is built around two things:
PSI (pressure) = what breaks dirt loose
GPM (flow) = what rinses it away
Your nozzle is what balances those two.
The size of the opening (orifice) in your nozzle directly controls how much pressure and flow you get.
Smaller nozzle = more pressure, less flow
Larger nozzle = less pressure, more flow
Why Nozzle Size Matters
If your nozzle is wrong, you’ll notice it immediately:
Low pressure? → Nozzle too big
Machine struggling? → Nozzle too small
Cleaning takes longer? → Wrong setup
Using the wrong nozzle can:
Reduce efficiency
Overwork your pump
Cause premature equipment failure
How to Actually Pick the Right Nozzle
There’s a formula, but you don’t need to memorize it:
Nozzle Size = GPM × √(4000 ÷ PSI)
Instead, most contractors use a chart.
Simple Way to Do It:
Find your machine’s PSI
Find your GPM
Match them on a nozzle chart
That gives you your correct orifice size
Example:
4 GPM @ 3000 PSI → ~4.5 nozzle
5.5 GPM @ 2500 PSI → ~7.0 nozzle
