Every pneumatic tool has a published air consumption figure. Every compressor has a published delivery figure. Matching the two is where most air systems go wrong, in both directions. This page gives you the real numbers from Chicago Pneumatic's own catalogs and the method for using them, including the parts that make the answer bigger than you expected.
Air tools are rated at 90 PSI measured at the tool inlet. Every figure below is Chicago Pneumatic's own published consumption at that condition, taken from the current General Industry and Power Technique catalogs. These are 100 percent load factor numbers, meaning the tool running continuously at full load.
| Tool type | Air at 90 PSI (cfm) | Typical | Models referenced |
|---|---|---|---|
| Percussive tools (chipping, scaling, needle) | 3 to 28 | 6.4 | 32 |
| Ratchet wrenches | 8.7 to 17 | 14 | 11 |
| Sanders and polishers | 2.5 to 80 | 17 | 115 |
| Screwdrivers and assembly tools | 8.5 to 30 | 19.5 | 8 |
| Die grinders | 2.1 to 86 | 21 | 59 |
| Drills | 3 to 80 | 23 | 19 |
| Impact wrenches | 10 to 84.5 | 31 | 51 |
| Angle grinders | 8 to 110 | 63 | 59 |
| Output drive | Air at 90 PSI (cfm) | What it is usually doing |
|---|---|---|
| 3/8 in | 10 to 20 | Light assembly, trim, small fasteners |
| 1/2 in | 15 to 25 | General maintenance and production fastening |
| 3/4 in | 24 to 53 | Heavy maintenance, fleet, structural |
| 1 in | 30 to 68 | Heavy industrial, mining, rail |
| 1-1/2 in | 60 to 85 | Large flange and structural bolting |
| 2-1/2 in | 75 | Heaviest industrial bolting |
| Tool | Class | Weight (lb) | Air at 90 PSI (cfm) |
|---|---|---|---|
| CP 0112 | Light breaker | 30 | 45 |
| CP 1210 | Light breaker | 35 | 48 |
| CP 1260 | Medium breaker | 60 | 63 |
| CP0030 | Diaphragm pump | 68 | 72 |
| CP 1290 | Heavy breaker | 90 | 81 |
The most common sizing mistake is summing the nameplate CFM of every tool in the shop. That assumes all of them run continuously at full load, which never happens, and it produces a compressor far larger than the plant needs.
The Compressed Air and Gas Institute defines load factor as the time factor multiplied by the work factor. Time factor is the percentage of the period the tool actually runs. Work factor is the percentage of full rated consumption the job actually demands. Multiply rated CFM by load factor to get average demand.
CAGI records pneumatic tools on production work measuring as little as 15 percent of the summed maximum rated consumption. A shop that sizes on the raw sum can end up with several times the compressor it needs, paying for it in capital and in part-load energy every year after.
Load factor gives you average demand, not peak. If three grinders genuinely run at once during a shift change or a weld-out, the system has to hold pressure through it. Average sizing with no allowance for simultaneous use is the failure mode in the other direction.
CAGI is explicit that guesses and rules of thumb should be avoided, and that the most accurate determination of load factor available should be used. Measured data from a similar plant beats a percentage someone remembers. This is the part we do on site rather than over the phone.
Tool demand is not total demand. Four things sit between the compressor and the tool, and every one of them has to be in the number before you choose a machine.
A healthy system leaks 5 to 10 percent of its supply per CAGI. Systems exceeding 30 percent are common and rarely noticed, because a leak is invisible until someone measures it. On a 200 CFM plant, 30 percent is 60 CFM going nowhere.
If a desiccant dryer is fitted, purge air can consume up to 15 percent of the dryer's rated capacity. That air is spent regenerating desiccant, not doing work, and it has to be generated by the compressor like everything else.
Tools are rated at 90 PSI at the inlet, not at the compressor. Undersized hose, restrictive couplings, clogged filters and long pipe runs all take pressure before the air arrives. A starved tool loses torque and speed while the compressor gauge still reads fine.
CAGI notes light breakers usually run 1/2 inch hose while medium and heavy breakers need 3/4 inch or 1 inch. Running a big tool down a small hose is one of the most common and most fixable causes of poor tool performance.
A fabrication shop runs six 1/2 inch impact wrenches at 20 CFM each and one large angle grinder. The instinct is that the impacts are the load and the grinder is incidental. The published figures say otherwise.
| Scenario | Working | Demand (cfm) |
|---|---|---|
| Six impacts, nameplate sum | 6 x 20 | 120 |
| Six impacts at 30 percent load factor | 120 x 0.30 | 36 |
| One angle grinder at top of range | continuous grinding | 110 |
| Grinder plus impacts at load factor | 110 + 36 | 146 |
| Add 10 percent for leaks on a healthy system | 146 x 1.10 | 161 |
Free air delivery is the figure that matters, and it is not always what the model number suggests. Chicago Pneumatic's portable range is a clear example, taken from the current Power Technique catalog.
| Model | Free air delivery (cfm) | Working pressure (psi) |
|---|---|---|
| CPS 110 | 95 | 100 |
| CPS 175-100 | 170 | 100 |
| CPS 185-100 | 180 | 100 |
| CPS 250-150 | 189 to 238 | 100 to 150 |
| CPS 400-150 | 350 to 400 | 100 to 200 |
How many CFM do I need to run an air impact wrench?
Chicago Pneumatic rates its industrial impact wrenches between 10 and 84.5 CFM at 90 PSI, depending on output drive. A 3/8 inch drive impact draws roughly 10 to 20 CFM, a 1/2 inch drive 15 to 25 CFM, a 3/4 inch drive 24 to 53 CFM, and a 1 inch drive 30 to 68 CFM. Those are 100 percent load factor figures, so a tool used intermittently averages far less.
Do I add up the CFM of all my tools to size a compressor?
No. Summing nameplate CFM assumes every tool runs continuously at full load, which oversizes the compressor. The correct method is load factor, which is the time factor multiplied by the work factor. The Compressed Air and Gas Institute notes that pneumatic tools on production work have measured as low as 15 percent of summed maximum rated consumption. Sizing on the sum alone wastes capital and energy.
Which air tool uses the most air?
Angle grinders. Chicago Pneumatic rates its industrial angle grinders from 8 to 110 CFM at 90 PSI, with a median of 63 CFM. That is roughly double the median impact wrench. A single large angle grinder can draw more air than several impact wrenches running together at realistic duty.
How much extra capacity should I allow for leaks?
A healthy compressed air system leaks 5 to 10 percent of its supply according to the Compressed Air and Gas Institute, but systems exceeding 30 percent are common. If a desiccant dryer is fitted, purge air can consume up to 15 percent of the dryer rated capacity. Both need to be in the calculation before you pick a compressor.
Why is my air tool underperforming even though the compressor is big enough?
Usually pressure drop rather than capacity. Air tools are rated at 90 PSI at the tool inlet, not at the compressor. Undersized or overlong hose, restrictive quick couplings, clogged filters and long pipe runs all drop pressure before the air reaches the tool. A tool starved of pressure loses torque and speed even when the compressor has capacity to spare. Call (844) 310-8665 and we can walk the system with you.
Tell us the tools you run, or the tools you are about to add, and we will work out what your compressor actually needs to deliver. We service and size compressed air systems across Southern California. Call (844) 310-8665 to reach us directly.
