The honest way to settle this is to look at what your tools draw, because the hose only matters relative to demand. Burst tools - nailers, impact wrenches, inflation - are not hose-limited at all in a garage, because the tank supplies the burst and the hose only has to refill it between pulls. An 18-gauge brad costs hundredths of a cubic foot per nail. A half-inch impact wrench averages 4.2 CFM at 90 PSI on Ingersoll Rand's published figure, and 3/8-inch hose carries that without complaint.
Continuous tools are where diameter starts to matter, and the line falls in a specific place. A quarter-inch die grinder sits at about 5 CFM on Ingersoll Rand's figures, with Engineering ToolBox giving a 4 to 6 CFM band - still comfortably within 3/8-inch territory. Orbital and disc sanders run 6 to 20 CFM continuous, and that is where 3/8-inch genuinely becomes the restriction rather than the pipe. Production spray guns sit in similar territory.
Which means the test is simple: if you own, or will own, a DA sander or a production spray gun, and a compressor that can actually feed one, you want 1/2-inch - in the drop, as plumbing. If your heaviest tool is an impact wrench, a ratchet, a die grinder or a touch-up gun, 3/8-inch is not a compromise and 1/2-inch buys you nothing. Most readers of this site are firmly in the second group, and the compressors on this site are the reason why.
Published air demand at 90 PSI| Tool | CFM @ 90 PSI | At load | Duty | What the number means |
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| Impact wrench, 1/2" | 4 - 5 | 22 | Burst | The most misunderstood number on this chart. Ingersoll Rand publishes 4.2 CFM average for the 231C and 22 CFM at load. The average assumes you hold the trigger for a second or two at a time. A 6-gallon pancake at 2.6 CFM does break lug nuts; it simply cannot keep the trigger down. |
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| Air ratchet, 3/8" | 3 - 4 | - | Intermittent | Ingersoll Rand publishes 3 CFM average at 90 PSI for the 105-D3; Engineering ToolBox lists 4 CFM for the class. A ratchet is the sneaky one: you hold the trigger far longer than with an impact, so it punishes a small tank harder despite the lower headline number. |
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| Die grinder, 1/4" | 5 - 6 | - | Continuous | Ingersoll Rand lists 5 CFM; Engineering ToolBox gives a 4-6 CFM band. Continuous duty, so a 6-gallon pancake gives you a handful of seconds before pressure drops and the tool slows. |
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| Orbital / DA sander, 6 inch | 10 - 9 | - | Continuous | Ingersoll Rand lists 10 CFM for a body orbital sander; Engineering ToolBox gives 6-9 CFM for the class. A sander runs continuously by nature, so there is no burst allowance to hide behind. This is the job that genuinely needs a big compressor. |
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| Vertical disc sander / polisher | 20 | - | Continuous | 20 CFM continuous. No portable garage compressor of any tank size will run this. If body work is the plan, price a 60-gallon two-stage before anything else. |
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| Paint spray gun, production / HVLP | 8 - 7 | - | Continuous | Ingersoll Rand lists 8 CFM for production spraying; Engineering ToolBox gives 3-7 CFM for small hand-operated sprayers. Check the gun's own spec sheet - HVLP demand varies more than any other tool class on this chart. |
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Where two references publish different figures, both are shown rather than averaged into a number nobody published. Primary sources: Ingersoll Rand air consumption chart, Engineering ToolBox air tool consumption, and per-tool manufacturer specifications.
