What Size Air Compressor Do I Need? CFM Calculator and Chart
You buy an air compressor once, then find out it cannot keep up with the tool you bought it for. The tank pressure drops, the tool slows down, and you stand around waiting for the motor to catch up. The fix is simple: size the compressor by CFM, not by tank gallons or horsepower.
Use the calculator below to find the CFM and tank size you need for the tools you actually run. Then read on for the three numbers that matter on any spec sheet.
Air Compressor Size Calculator
Pick your tools. Get the CFM at 90 PSI and the tank size to shop for.
Tool figures are typical CFM ranges at 90 PSI from published air tool charts. The calculator uses a middle value for each tool. Always check the rating printed on your own tool.
CFM at 90 PSI is the number that matters
CFM means cubic feet per minute. It tells you how much air the pump can deliver, and most air tools are rated at 90 PSI. If your compressor delivers less CFM than your tool uses, the tank slowly empties and the tool loses power.
Watch the fine print. Many boxes show CFM at 40 PSI because it is a bigger number. Compare compressors only by their CFM at 90 PSI.
Air tool CFM chart
These are typical ranges at 90 PSI. Brands vary, so treat them as a starting point and confirm with the tool you own.
| Air tool | Typical CFM at 90 PSI | Use pattern | Suggested tank |
|---|---|---|---|
| Brad or finish nailer | 0.5 to 2 | Short bursts | 2 gal and up |
| Framing or roofing nailer | 2 to 4 | Short bursts | 6 gal and up |
| Tire inflator or blow gun | 1 to 3 | Short bursts | 2 gal and up |
| 3/8 in. air ratchet | 3 to 5 | Short bursts | 6 gal and up |
| 1/2 in. impact wrench | 4 to 8 | Short bursts | 10 gal and up |
| Air hammer or chisel | 3 to 6 | Bursts | 6 gal and up |
| Die grinder or cut off tool | 5 to 8 | Continuous | 20 gal and up |
| DA or orbital sander | 6 to 9 | Continuous | 20 gal and up |
| HVLP touch up gun | 4 to 8 | Continuous | 20 gal and up |
| Full size HVLP spray gun | 8 to 18 | Continuous | 30 gal and up |
Add a margin, then add tools together
The common rule is to take your hungriest tool and multiply its CFM by 1.5. That margin covers worn fittings, long hoses and the tool you will buy next year.
If two people or two tools run at the same time, add their CFM together first. A 1/2 inch impact wrench at 5 CFM plus a tire inflator at 2 CFM means you need at least 7 CFM, plus a buffer.
How big a tank do you need?
The tank is a buffer, not a power source. A bigger tank lets the motor rest between nail shots, but it cannot make up for a pump that is too small.
- 1 to 3 gallons: brad nailers, airbrushes and topping up tires.
- 6 to 10 gallons: framing nailers, occasional impact wrench use and most home garage jobs.
- 20 to 30 gallons: sanders, grinders and spray guns that run without stopping.
- 60 to 80 gallons: body work, full size spray guns and shops where two people work at once.
Duty cycle and power supply
Duty cycle is how much of the time the pump can run before it needs to cool down. Nailers and ratchets are fine with a 50% duty cycle, but grinders and sanders need 75 to 100% if you use them for long stretches.
Most portable compressors run on a standard 120V outlet. Large stationary compressors usually need a dedicated 240V circuit, so plan the wiring before you buy. If you must use a cord, size it with our extension cord gauge calculator so the motor does not starve.
Three common garage setups
| Your setup | CFM at 90 PSI to look for | Tank |
|---|---|---|
| Trim work, crafts and tire top ups | 3 CFM | 2 to 6 gal |
| Framing nailer plus tire changes with an impact wrench | 7 to 8 CFM | 10 to 20 gal |
| Sanding, grinding or painting a car | 10 to 15 CFM | 30 to 80 gal |
Ready to buy? Our best air compressors for home garage use lists each pick’s CFM at 90 PSI, tank size and noise level, so you can match it to your number.
If you only change wheels, compare air tools with the best cordless impact wrenches for lug nuts and the best cordless tire inflators. Cordless tools skip the compressor entirely.
Planning to cut metal with plasma? Most plasma cutters need clean, dry compressed air, so check the CFM rating in our best plasma cutters for metal fabrication guide before you size your compressor.
Frequently Asked Questions
What size air compressor do I need for an impact wrench?
A typical 1/2 inch impact wrench uses 4 to 8 CFM at 90 PSI. Look for a compressor that delivers at least 6 to 8 CFM at 90 PSI with a tank of 10 gallons or more.
Is a 6 gallon air compressor big enough for a garage?
For nailers, tire inflation and blowing off parts, yes. For sanders, grinders and spray guns, no, because those tools need more CFM than most 6 gallon pancake compressors can deliver.
Does a bigger tank mean more power?
No. The tank only stores air. The pump’s CFM rating decides whether a tool can run continuously, while the tank decides how long you can work before the motor restarts.
What size air compressor do I need to paint a car?
A full size HVLP spray gun can use 8 to 18 CFM at 90 PSI. Most people painting a whole car use a 60 to 80 gallon stationary compressor, usually on a 240V circuit.
What is the difference between CFM and SCFM?
SCFM is CFM measured at standard air conditions, so it is easier to compare between brands. For shopping, treat them the same, and always compare the rating at 90 PSI.
Also Read On:
Best Air Compressors for Home Garage (2026 Picks)
