Air compressor sizing calculator
Pick the tools you run at the same time and this totals the demand and adds headroom. Duty cycle matters: a nailer that fires once every few seconds draws far less average air than its peak figure, while a sander or a blast cabinet runs continuously.
- Compressor needed
- 24.0 CFM at 90 psi
Tools total 16.0 CFM, plus 50 percent headroom because at least one tool runs continuously. Buy on delivered CFM, not horsepower or tank size.
Air tool CFM chart
These are typical consumption figures at 90 psi. Continuous-duty tools are the ones that size the compressor; intermittent tools average out well below their peak.
| Tool | CFM at 90 psi | Duty |
|---|---|---|
| Blow gun | 3 to 5 | Intermittent |
| Framing nailer | 2 to 3 | Intermittent |
| Air ratchet | 3 to 5 | Intermittent |
| 1/2 in impact wrench | 4 to 5 | Intermittent |
| 3/4 in impact wrench | 7 to 10 | Intermittent |
| Air hammer / chisel | 4 to 5 | Intermittent |
| Die grinder | 4 to 6 | Continuous |
| Cut-off tool | 4 to 6 | Continuous |
| Angle grinder (7 in) | 5 to 8 | Continuous |
| Orbital sander | 6 to 9 | Continuous |
| Dual action sander | 10 to 13 | Continuous |
| HVLP spray gun | 10 to 14 | Continuous |
| Needle scaler | 8 to 16 | Continuous |
| Small sandblast cabinet | 15 to 25 | Continuous |
| Plasma cutter (40 A) | 4 to 7 | Continuous |
What CFM means on an air compressor
CFM is cubic feet per minute of air delivered. The number only means something with a pressure attached, because a compressor delivers more CFM at 40 psi than at 90. Always compare figures at the same pressure, and 90 psi is the standard reference for air tools.
Horsepower is not a substitute. Two 5 hp compressors can differ by 30 percent in delivered CFM depending on whether they are single or two stage and how fast the pump turns. Buy on CFM at 90 psi and treat horsepower as a rough sanity check.
As a guide, a good two-stage industrial pump delivers around 4 CFM per horsepower at 90 psi. A single-stage direct-drive unit is nearer 3 to 3.5.
SCFM to CFM conversion
SCFM is airflow corrected to standard conditions, which the industry takes as 14.7 psia, 68 degrees F and 36 percent relative humidity. ACFM is the actual volume at the conditions where it is measured. CFM used loosely on a spec sheet usually means SCFM.
The conversion is SCFM = ACFM x (P_actual / 14.7) x (528 / T_actual in Rankine). At sea level and room temperature the two are close, but at altitude the gap widens: at 5,000 feet a compressor delivers roughly 15 percent less SCFM than its sea-level rating.
When comparing two machines, check both are quoting SCFM at the same pressure. A spec sheet quoting displacement CFM rather than delivered SCFM will overstate capacity by 25 percent or more.
