Becoming experienced in regards to the art of pressure washing requires proper understanding of the important concepts and units of measurement.

Things like gallons per minute (GPM) which indicates relative water consumption, and clean units which is a measure of the performance or efficiency of a particular unit.

These values are important for customers, business owners and operators to be familiar with.

There is however one more unit of measurement that is arguably the most important to understand in order to operate a pressure washer safely and effectively.

PSI (pressure per square inch), which alongside GPM allows us to calculate clean units, is in many ways the most crucial factor for pressure washer operators to understand.

As the name itself explains, pressure washers are characterized by the water pressure that they produce, and the quality cleaning power that they produce as a result.

Let’s discuss what PSI is, why it matters, and how to determine the right PSI for your pressure washing needs.

What Is PSI?

What is PSI

PSI is a unit measurement of pressure that is expressed as pounds of force per square inch, also known as PSI.

This is the most commonly used unit for measuring pressure in North America. There are two other variations of PSI that are also commonly used, but instead of a general pressure measurement, they are used to denote specific pressure measurements.

PSIG is the unit term used to denote pressure that is specified by a gauge or other device that is used to measure pressure. This unit provides useful information about the difference between the pressure in a pipe or pressurized tank of some sort and the atmosphere around it.

PSIA is the unit term used to describe the absolute pressure in PSI, which includes the pressure of the atmosphere. It is often referred to as “total pressure”.

Why Does It Matter?

Why is PSI important

In general, PSI is an incredibly important concept to understand for a number of different industries and applications.

When it comes to pressure washing, pounds of force per square inch is arguably the most important specification to consider when choosing the right pressure washer for your needs.

Homeowners who are simply looking to purchase a machine that they can use to clean their house’s siding once or twice a year won’t need an incredibly high power (or high PSI) unit.

Commercial pressure washing businesses on the other hand, who are taking on large scale jobs on a daily basis, will most likely need to be purchasing pressure washers that offer high PSI capabilities.

It is important to evaluate the relative size and extent of cleaning that your pressure washing jobs will require.

Are you dealing with high volumes of square footage and multiple story buildings? Are the surfaces to be cleaned showing extensive dirt and grime buildup?

These questions will help indicate what kind of pressure washing machine you should be looking at purchasing, in terms of the pounds of force per square inch that the machine can provide. Large jobs where you are taking on heavy grime will always be more efficiently tackled with a high PSI pressure washer.

Not only does PSI matter in terms of cleaning power and choosing the appropriate machine for specific jobs, but it is also important for health and safety reasons.

High PSI pressure washers have jet streams that can potentially cause significant damage to human skin and other organs, especially the eyes. It is incredibly important to be aware of your machine’s jet stream pressure potential, and to always wear the appropriate protective gear to prevent injuries.

Closed toed shoes, long pants and shirts that cover all exposed skin, and a full coverage pair of safety glasses are the most important  protective items to have when pressure washing.

How To Determine The Right PSI For Your Pressure Washer

How To Determine The Right PSI For Your Pressure Washer

Choosing the right PSI for your pressure washer is an imperative part of achieving that perfectly clean, brand new look on all of your surfaces.

It is important to consider the type and extent of the stains that you are removing, but more importantly, the type of surface that you are cleaning will most of the time be your appropriate PSI indicator.

Let’s outline a few of the PSI guidelines for a variety of surfaces that are commonly cleaned with a pressure washer.

Car or Truck

Recommended PSI Range: 1200 – 1900 PSI

See how to clean your car or truck with a pressure washer

Patio Furniture

Recommended PSI Range: 1500 – 1900 PSI

See how to clean patio furniture with a pressure washer


Recommended PSI Range: 2900 – 3200 PSI


Recommended PSI Range: 2000 – 2800 PSI

See how to clean your fence with a pressure washer


Recommended PSI Range: 2900 – 3200 PSI

See how to clean your driveway with a pressure washer

Heavy Stain Removal

Recommended PSI Range: 3300 + PSI (if surface will not be damaged)


Choosing the right pressure washer for your cleaning needs, whether it is a homeowner looking for a simple unit or a business owner in need of a heavy duty cleaning machine, PSI (pounds force per square inch) is one of the most important specifications to consider.

We have discussed what exactly PSI means from a general definition standpoint, as well as why it matters specifically for pressure washing situations.

Important aspects like relative machine cleaning power and health and safety factors related to PSI were also briefly covered, as these are the most commonly considered. We were able to convey why PSI is such a crucial consideration for business owners and machine operators alike.

Finally, we discussed a little bit about how to determine the right PSI for your pressure washer in relation to the jobs at hand.

We were also able to provide a breakdown of some of the common surfaces that pressure washers are used for, and the recommended PSI ranges that will provide the most effective and efficient clean for each.

Consider this advice and these guidelines when perfecting your pressure washers PSI settings in order to ensure a safe and successful cleaning experience.

More from PressureWashr