How to Choose the Right Nozzle Size (And Why It Matters)

How to Choose the Right Nozzle Size (And Why It Matters)

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:

  1. Find your machine’s PSI
  2. Find your GPM
  3. Match them on a nozzle chart
  4. That gives you your correct orifice size

Example:

  • 4 GPM @ 3000 PSI → ~4.5 nozzle
  • 5.5 GPM @ 2500 PSI → ~7.0 nozzle

Here is the easiest nozzle calculator to use: Nozzle Calculator

Here is a full video and how to pick the right nozzle using the nozzle chart. 

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