Start with the exact tool's published air consumption and the compressor's rated delivery at the required pressure. Matching the two takes more than adding nameplate figures. This page uses Chicago Pneumatic's catalog data and a practical sizing method, including operating patterns and system losses that can change the answer.
Use the exact tool's specified inlet pressure and air-consumption condition. The industrial tables below summarize an audited sample from CP's General Industry catalog, revision v6.08.2026, at 90 PSI (6.3 bar). Most entries are consumption under load; the screwdriver entries are free-speed consumption. These conditions are different, and neither a sample median nor a duty-cycle estimate replaces the exact tool specification.
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| Tool type | Air at 90 PSI (cfm) | Sample median | Included variants |
|---|---|---|---|
| Percussive tools | 0.2 to 28 | 14 | 20 |
| Ratchet wrenches | 10 to 21 | 14 | 14 |
| Sanders and polishers | 6 to 91 | 18 | 124 |
| Screwdrivers and assembly tools (free speed) | 8.5 to 30 | 21 | 17 |
| Die grinders | 2.1 to 55 | 23 | 116 |
| Drills | 12 to 110 | 29 | 44 |
| Impact wrenches | 10 to 84.5 | 30 | 64 |
| Angle grinders | 8 to 80 | 40 | 54 |
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| Output drive | Air at 90 PSI (cfm) | What it is usually doing |
|---|---|---|
| 3/8 in | 10 to 20 | Light assembly and smaller fasteners |
| 1/2 in | 13 to 30 | Maintenance and production fastening |
| 3/4 in | 24 to 52.9 | Heavy maintenance and fleet work |
| 1 in | 30 to 68 | Heavy industrial fastening |
| 1-1/2 in | 60 to 84.5 | Large flange and structural bolting |
| 2-1/2 in | 74.9 | Large industrial bolting |
| 7/16 in | 10 | Hex output; keep separate from square drive |
| #5 spline | 48 to 68 | Spline output; keep separate from square drive |
Summing the nameplate CFM of every tool assumes all of them run continuously at full load. Check whether that matches actual operation. Intermittent use can make average demand much lower, while simultaneous use still determines the peaks the system must support.
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 describes one plant where 434 production tools consumed 15 percent of their summed maximum ratings. That measured case illustrates why actual use matters. It is not a default load factor for another plant.
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.
Method reference: CAGI Compressed Air & Gas Handbook, Chapter 4, pages 2–6. Confirm model-specific tool consumption, compressor delivery and operating conditions before making a final selection.
Further reading: Compressed Air Best Practices: Matching Supply and Demand explains why demand changes, available storage and minimum delivered pressure need to be considered together.
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.
CAGI says a healthy system should not leak more than 5 to 10 percent of its supply; some systems exceed 30 percent. Measure your losses rather than treating either figure as a target or allowance. On a 200 CFM plant, 30 percent is 60 CFM going nowhere.
Regenerative desiccant dryers can use compressed air for purge. Confirm the selected model's demand at the operating conditions and include it in a calculated estimate. If a system assessment already measured total demand including purge and leaks, do not add those loads a second time.
Check pressure at the tool inlet while it operates against the manufacturer's specified requirement. Undersized hose, restrictive couplings, clogged filters and long pipe runs can reduce delivered pressure. A starved tool can lose torque and speed while the compressor gauge still reads normally.
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.
This illustrative shop uses six impact wrenches assumed to consume 20 CFM each under load and one CP3850-60AB9V angle grinder, listed at 80 CFM under load in the linked catalog (page 143). The assumed impact duty cycle is 30 percent and the grinder runs continuously. Verify these inputs for the actual tools and work pattern.
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| 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 CP3850-60AB9V angle grinder | continuous grinding at catalog consumption | 80 |
| Grinder plus impacts at load factor | 80 + 36 | 116 |
| Illustrative allowance: add 10% of tool demand (not 10% of total supply) | 116 x 1.10 = 127.6 | 128 (rounded up) |
Free air delivery is the figure that matters, and it is not always what the model number suggests. Check the exact model version and working pressure when comparing portable compressors.
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| 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 | Confirm exact variant | Confirm exact variant |
How many CFM do I need to run an air impact wrench?
The included catalog sample spans 10 to 84.5 CFM under load at 90 PSI. Its square-drive groups span 10 to 20 CFM for 3/8 inch, 13 to 30 for 1/2 inch, 24 to 52.9 for 3/4 inch, and 30 to 68 for 1 inch. These are ranges among included variants, not a rating for every CP tool. Check the exact part number, operating condition and required inlet pressure; average use also depends on the actual duty cycle.
Do I add up the CFM of all my tools to size a compressor?
Summing nameplate CFM assumes every tool runs continuously at full load. Check actual simultaneous use and load factor before choosing a compressor. CAGI reports one plant where 434 tools consumed 15 percent of their summed maximum ratings. That is a case example, not a sizing factor for your facility. Average demand and peak requirements both need to be met.
Which air tool uses the most air?
Large drills and vertical grinders can be major loads: the catalog lists CP1820R32 and CP3340-SALAVAD at 110 CFM under load. The included angle-grinder sample spans 8 to 80 CFM, with a sample median of 40 CFM. That median describes the included variants; it is not a sizing allowance or a ranking of every tool. Compare the exact models and simultaneous operating pattern.
How much extra capacity should I allow for leaks?
CAGI says a healthy system should not leak more than 5 to 10 percent of its supply; some systems exceed 30 percent. Measure the actual losses rather than using those figures as an allowance. Confirm any regenerative dryer purge demand for the selected model. Include leaks and purge in a calculated demand estimate, but do not add them again if they are already captured in measured total demand.
Why is my air tool underperforming even though the compressor is big enough?
Pressure drop can limit performance even when compressor capacity is sufficient. Check pressure at the tool inlet while it operates against the manufacturer's requirement. Undersized or overlong hose, restrictive couplings, clogged filters and long pipe runs can reduce delivered pressure. Check tool condition and actual simultaneous demand as well. Call (844) 310-8665 and we can walk the system with you.
Tell us the tools you run, their quantities, which run together and how often, plus any planned additions. Include rated air consumption and required inlet pressure where available, your site's ZIP code, and the available voltage and phase if you are selecting stationary equipment. Share what you know in the form below; final sizing depends on the equipment specifications and actual operating conditions. We service and size compressed air systems across Southern California. Call (844) 310-8665.
