Set it by the tool
An independent reference on compressed-air pressure: tool ratings, regulator settings and compressor sizing rules, compiled from published standards and standard workshop practice.
Not a store, not a compressor brand, not a repair service. Nothing here is sold, booked or serviced, and no manufacturer or retailer stands behind this text.
For most air tools the outlet should be set so the tool sees 90 psi (6.2 bar) at its inlet — in practice 100-110 psi on the regulator gauge, while the tank runs up to its 125-175 psi cut-out on its own.
A workshop compressor has two pressure gauges and they answer different questions. The tank gauge shows stored pressure: the pressure switch lets the tank charge until it hits cut-out, somewhere between 125 and 175 psi on standard machines, and that number is not set by hand. The outlet gauge shows what actually leaves for the hose, and that is the number the question is really about.
Most air tools are rated to run at 90 psi measured at the tool. Because every run of hose and every quick-connect fitting costs pressure, the regulator is normally set 10-20 psi above the rating so the tool still sees its full 90 psi while it is working. For a 90-psi tool, a starting point of 100-110 psi on the outlet gauge is the usual workshop practice.
The exceptions matter more than the rule. A brad nailer may be happy anywhere in a 60-100 psi window, a framing nailer wants 100-120 psi, an HVLP spray gun is legally defined by a 10-psi ceiling at the air cap, and a blow gun used for cleaning is capped at 30 psi by OSHA when no chip guard is fitted. The tool's rating plate or manual always outranks the generic 90-psi figure.
Each tool family has its own pressure window, and the spread between them is wide enough that one setting never fits all.
Nailers show the spread clearly. Brad nailers typically run at 60-100 psi, while framing nailers commonly need 100-120 psi to drive full-length nails into framing lumber — a gap at the top end that decides whether nails seat flush or stand proud.
Spray equipment sits at the extremes. Under the EPA definition, an HVLP gun must deliver 10 psi or less at the air cap and still achieve at least 65% transfer efficiency; conventional air spray runs at 40-60 psi. Setting an HVLP gun by the compressor's usual 90-psi habit would break both its finish quality and its legal definition.
The full chart with airflow figures lives on the Air Tool Pressure and CFM Chart page; the quick reference below covers the settings most often asked about.
| Tool or task | Pressure setting | Where it is measured | Notes |
|---|---|---|---|
| Most air tools (general) | 90 psi (6.2 bar) | Tool inlet | Set the regulator 10-20 psi higher to cover hose and fitting losses |
| Brad nailer | 60-100 psi | Tool inlet | Stay within the range marked on the tool |
| Framing nailer | 100-120 psi | Tool inlet | Needed to drive full-length nails into framing lumber |
| 1/2-inch impact wrench | 90 psi | Tool inlet | Draws about 2.5-5 CFM at 90 psi |
| HVLP spray gun | 10 psi or less | Air cap | EPA definition also requires at least 65% transfer efficiency |
| Conventional spray gun | 40-60 psi | Gun inlet | Conventional air spray, not subject to the HVLP cap |
| Blow gun for cleaning | 30 psi maximum | Nozzle, effective | OSHA 1910.242(b) when no chip guarding is fitted |
| Passenger car tires | 30-35 psi | Cold tire | Use the driver's door jamb placard, not the sidewall maximum |
The whole adjustment takes a few minutes, and doing it in order prevents the two classic failures: a tool starved by pressure sag and a gauge read at the wrong moment.
Work from the tool backward, not from the tank forward. The rating on the tool tells you the target; the regulator's job is to deliver that target at the inlet while air is flowing, which is why the final check is done with the tool running.
Two failure modes account for most bad setups. Setting by the tank gauge leaves the tool under-fed, because the tank number says nothing about the outlet. Setting the outlet with the tool idle and never re-checking it under load misses pressure sag — the gauge can drop the moment the tool starts drawing air.
If the outlet sags below the rating even at a higher setpoint, the bottleneck is elsewhere: too much hose, restrictive fittings, or a compressor whose CFM cannot keep up. The sizing rules on Choosing a Compressor by CFM and Tank Size cover that case.
The figures cited on this page trace to tool manufacturers' rating conventions, the EPA HVLP definition, OSHA 1910.242(b) and standard compressor specifications.