Shop Air Compressors by Horsepower
Horsepower is the size of the motor, not the amount of air. It is still the number most people start from, because it is the number on the nameplate of the compressor they are replacing and it tells you roughly what power service the machine needs. Every compressor we sell is listed below by its motor horsepower so you can start there, then check the CFM and pressure on the product page before you buy. If you already know the flow or pressure you need, start from Shop by CFM or Shop by PSI instead.
Pick a horsepower
- 2 HP air compressors: 4 to 7 CFM, 115 volt garage and trim units, quiet oil free California Air Tools, Champion R-Series in 2 HP trim.
- 3 HP air compressors: 7 to 11 CFM, two stage piston, small rotary screw and oil free scroll. 230 volt.
- 5 HP air compressors: 14 to 19 CFM, the standard two stage shop compressor on 60 or 80 gallon tanks, single or three phase.
- 7.5 HP air compressors: 22 to 26 CFM piston, 26 to 41 CFM rotary screw. The top of single phase.
- 10 HP air compressors: 32 to 48 CFM, two stage simplex, duplex packages and 10 HP rotary screws.
- 15 HP air compressors: 45 to 81 CFM, the largest simplex piston size and the start of plant rotary screws.
- 20 HP air compressors: 78 to 106 CFM, rotary screw becomes the default; duplex piston and scroll for special cases.
- 25 HP air compressors: 100 to 138 CFM stationary screws plus the 110 CFM towable and utility mount class.
- 30 HP air compressors: 114 to 134 CFM fixed speed, up to 208 CFM variable speed.
- 40 HP air compressors: 161 to 234 CFM gear drive and variable speed rotary screws.
- 50 HP air compressors: 219 to 277 CFM plant air, plus the 185 CFM diesel utility mount.
- 60 HP air compressors: 248 to 321 CFM, gear drive and permanent magnet variable speed.
Range pages: under 5 HP, 5 to 15 HP piston, 15 to 30 HP, over 30 HP, and for rotary screws 0 to 20 HP, 20 to 50 HP and 50 HP and up. Need 75 HP or more? The Chicago Pneumatic CPI and CPV lines run to 120 HP and are listed under 50 HP and up rotary screw air compressors; contact us for anything larger.
What horsepower actually tells you
A rule of thumb is 4 to 5 CFM per horsepower at 100 PSI for a rotary screw, 3.5 to 4 CFM per horsepower at 175 PSI for a two stage piston, and 2 to 3 CFM per horsepower for a single stage or oil free piston. That is why a 5 HP two stage makes about 17 CFM, a 5 HP rotary screw about 18 CFM, and a 2 HP oil free unit about 5 CFM. The spread gets wider at larger sizes: a 30 HP fixed speed screw makes 134 CFM at 100 PSI while a 30 HP variable speed unit on a bigger airend makes 208 CFM, because the drive lets the airend run at whatever speed the motor can carry at that pressure. Match CFM at your working pressure first and horsepower second, or you will end up with the same horsepower as the old machine and less air.
Single phase or three phase
Up to 5 HP, almost every compressor is available in 230 volt single phase, and 2 HP units run on 115 volt. 7.5 HP is the practical ceiling for single phase; the units exist, but they draw 35 to 40 amps and need a 60 amp circuit and a magnetic starter. From 10 HP up, three phase is the norm and 460 volt is standard from about 25 HP. Typical full load amps at 460 volt three phase: 10 HP 14 A, 15 HP 21 A, 20 HP 27 A, 25 HP 34 A, 30 HP 40 A, 40 HP 52 A, 50 HP 65 A, 60 HP 77 A. Double those figures for 230 volt three phase. Variable speed compressors ship with their own drive and need no separate starter.
Where piston stops and rotary screw starts
Two stage piston compressors are the lowest cost per CFM from 2 to 15 HP and are built for 50 to 60 percent duty: they fill a tank, shut off and cool. Rotary screws run 100 percent duty at 65 to 72 dBA and become the mainstream choice at 7.5 to 10 HP, the default at 20 HP, and the only stationary option above 30 HP apart from duplex piston sets bought for redundancy. Oil free scroll compressors run from 2 to 60 HP in cabinets of one to several scroll pumps and are the choice for dental, lab, pharmacy, food and instrument air. Duplex piston sets at 10 to 60 HP pair two pumps on one tank with alternating controls so the plant keeps running when one pump is down.
Receivers and dryers by size
Plan on 60 to 80 gallons of receiver for a 5 HP piston, 120 gallons at 10 HP, 240 gallons at 20 to 25 HP, 400 gallons at 40 HP and 660 gallons at 60 HP; variable speed screws can run on about half those volumes. Size the refrigerated air dryer to the compressor output at your inlet temperature, not to the tool, and use the dryer CFM calculator if the compressor room runs hot.
Not sure which size you need? Call or chat with the tools or the process you run and the power you have, and we will size the compressor, receiver and dryer together.
