What is a normal cut-in and cut-out for a shop compressor?

A common setting is 95 psi cut-in and 125 psi cut-out, a 30 psi differential; never set cut-out above the tank's rated working pressure.

What happens if the differential is too small?

The compressor short-cycles, which overheats the motor, wears contacts and starters, and shortens compressor life.

Which screw changes cut-out versus differential?

The large range nut moves both cut-in and cut-out together; the smaller differential nut changes only the cut-in point on most Square D and Condor switches.

Air Compressor Pressure Switch Cut-In / Cut-Out Calculator

All calculators

Formula

Differential = Cut-out − Cut-in · Starts/hr = 60 ÷ (Run + Off)

What do you want to calculate?

Cut-out (motor stops)

psi

Differential

psi

Cut-in

100psi

Cut-out

125psi

Differential

25psi

Cut-in ratio

80%

of cut-out

Verify: motor starts per hour

Tank MAWP

psi

Tank size

gal

Pump output

cfm

Avg demand

cfm

Motor duty class (max starts/hr)

Run time

2.6min

Off time

2.3min

Starts / hour

12.3

Duty cycle

53%

Too many starts (12.3/hr > 10)

Widen the differential, add a larger receiver, or fit an auto-drain and constant-speed unloader. See the receiver sizing calculator.

Field procedure

Disconnect power and lock out. Bleed tank to 0 psi.
Remove switch cover. Identify the large range spring and small differential spring.
Restore power. Let compressor pump up. Note actual cut-out on gauge.
Bleed slowly through an outlet. Note actual cut-in.
Range screw CW = raise both settings. Differential screw CW = widen the gap.
Re-test one full cycle. Confirm relief valve does not pop at cut-out.
Time one full cycle with a stopwatch and compare to the "starts / hour" result above.
Replace cover.

How to use this calculator

Work out cut-in, cut-out and differential settings for an air compressor pressure switch.

Enter the desired cut-out (stop) pressure.
Enter the desired cut-in (start) pressure or the differential.
Read the resulting differential and check it against the switch's adjustable range.
Adjust the range nut first, then the differential nut, and verify with a gauge over a full cycle.

Frequently asked questions

What is a normal cut-in and cut-out for a shop compressor?: A common setting is 95 psi cut-in and 125 psi cut-out, a 30 psi differential; never set cut-out above the tank's rated working pressure.
What happens if the differential is too small?: The compressor short-cycles, which overheats the motor, wears contacts and starters, and shortens compressor life.
Which screw changes cut-out versus differential?: The large range nut moves both cut-in and cut-out together; the smaller differential nut changes only the cut-in point on most Square D and Condor switches.