Home & DIY
What size air compressor do you need (CFM)?
Air compressor CFM and tank size from the air tools you run, with a safety margin and single vs two-stage guidance.
Quick answer
An air compressor is sized by CFM — the air flow it delivers at 90 PSI — because that is the only number that decides whether it can actually run your tools. The rule: add up the CFM of every tool you run at the same time, or, if you work one tool at a time, just take your thirstiest single tool; then add 50% headroom so the motor isn’t pinned at maximum. Example: a 1/2" impact wrench needs about 5 CFM, so 5 × 1.5 ≈ 7.5 CFM is the compressor to look for. Horsepower and tank gallons are marketing noise next to CFM.
Which air tools will you run?
Recommended compressor
7.5 CFM @ 90 PSI
- Your peak air demand
- 5 CFM
- Suggested tank
- Small is fine (24-50 L / 6-13 gal)
CFM (air flow at 90 PSI) is the only number that decides whether a compressor can run your tools — not horsepower, not gallons. Add the CFM of tools you run at the same time (or take the thirstiest single tool if you work one at a time), then add 50% headroom so the motor isn’t maxed out. A bigger tank does NOT add CFM: it just stores air so the motor cycles less during short bursts (nailing, inflating). Continuous tools — sanders, grinders, spray guns, sandblasters — drink air non-stop, so they need real CFM, not a big tank to hide behind. Match the CFM to your hungriest tool and you’re set.
How it works
Two things beyond CFM. Tank size decides how the compressor behaves, not whether it copes: for burst tools like a brad nailer a small tank is fine, but continuous tools — sanders, spray guns, a sandblaster — drain any tank in seconds, so they need real CFM, not a big reservoir to hide behind. And stage: single-stage compressors are cheaper and fine for most home tools; two-stage units hold higher pressure for continuous or heavy shop use. Match the CFM to your hungriest tool, pick a tank that suits burst vs continuous work, and don’t overpay for horsepower numbers.
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Frequently asked questions
CFM, horsepower or gallons — which one matters?+
CFM, by a mile. CFM is the actual air flow the compressor delivers, and it is what your tools consume — if a tool needs 6 CFM and the compressor delivers 4, it simply won’t keep up, no matter the horsepower. Gallons (tank size) only change how long you can burst before the motor catches up; horsepower is loosely related to CFM but manufacturers inflate it. Always compare tool CFM to compressor CFM at the same PSI (usually 90 PSI).
What size compressor for a spray gun or sanding?+
Big, because these are continuous tools that draw air non-stop. An HVLP spray gun needs about 6 CFM and an orbital sander 8-9 CFM, so with the 50% margin you want roughly 9-14 CFM continuous — realistically a stationary belt-drive compressor with a 100+ liter tank, not a portable pancake. A small compressor will run constantly, overheat and still starve the tool. For continuous work, buy CFM first and tank second.
Does a bigger tank give more CFM?+
No. The tank stores compressed air but doesn’t create it — CFM comes from the pump and motor. A big tank helps with short bursts (a nail gun, inflating a tire) because it holds a reserve so the motor cycles less often. But for continuous tools the reserve empties in seconds and you’re left with whatever CFM the pump can produce. Bigger tank = fewer motor starts on burst work; it never turns a weak compressor into a strong one.
What size for just a nail gun or inflating tires?+
Tiny. Brad nailers and tire inflators are burst tools drawing 2-3 CFM for a fraction of a second, so a small portable "pancake" compressor (around 6 gallons / 24 liters, 2-3 CFM) is plenty and easy to carry. You only need to size up if you add continuous tools like sanders or spray guns. For trim work, tire care and occasional DIY, don’t overbuy — a compact unit is quieter, cheaper and does the job.
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