Standard cubic feet per minute (SCFM) and cubic feet per minute (CFM) are both units used to calculate or measure air flow rates. SCFM and CFM are calculated differently and are commonly employed within the air compressor industry. This article explains the distinction between them, details the conversion between SCFM and CFM, and provides a brief explanation of ACFM.
1. “Standard” air flow rate in cubic feet per minute.
2. Measurement conditions: will be measured in a standard state, such as fixed temperature, humidity and pressure as a standard state.
3. An example of a commonly used US standard (with minor variations):
Temperature 68°F (20°C): close to the global average room temperature, excluding the effects of thermal expansion and contraction.
Humidity 0%: eliminates water vapor interference with air density
Pressure 14.7 psi: Standard atmospheric pressure at sea level to establish a uniform datum
Note: ISO standard is 15°C/0% RH, industry needs to specify the standard used.
1. how many cubic feet of air flow per minute
2. There is no specification on what temperature, humidity and pressure to measure under.
3. So the same air compressor in different conditions measured CFM results will have a big difference
Assuming that the same Elang air compressor is used under different conditions:
Measured CFM = 110 in summer (high temperature and low pressure)
Converted from the standard condition, probably SCFM = 100
CFM > SCFM, which means that the actual air density in the measurement environment is lower than the standard density.
| Pressure (psig) | Temperature (°F) | Conversion Factor (SCFM per CFM) | SCFM (for 100 CFM) |
|---|---|---|---|
| 30 | 60 | 3.088 | 308.8 (CFM to SCFM) |
| 30 | 70 | 3.029 | 302.9 (CFM to SCFM) |
| 30 | 80 | 2.973 | 297.3 (CFM to SCFM) |
| 30 | 90 | 2.919 | 291.9 (CFM to SCFM) |
| 30 | 100 | 2.867 | 286.7 (CFM to SCFM) |
| 40 | 60 | 3.778 | 377.8 (CFM to SCFM) |
| 40 | 70 | 3.707 | 370.7 (CFM to SCFM) |
| 40 | 80 | 3.638 | 363.8 (CFM to SCFM) |
| 40 | 90 | 3.572 | 357.2 (CFM to SCFM) |
| 40 | 100 | 3.508 | 350.8 (CFM to SCFM) |
| 50 | 60 | 4.469 | 446.9 (CFM to SCFM) |
| 50 | 70 | 4.385 | 438.5 (CFM to SCFM) |
| 50 | 80 | 4.304 | 430.4 (CFM to SCFM) |
| 50 | 90 | 4.225 | 422.5 (CFM to SCFM) |
| 50 | 100 | 4.15 | 415.0 (CFM to SCFM) |
| 60 | 60 | 5.16 | 516.0 (CFM to SCFM) |
| 60 | 70 | 5.062 | 506.2 (CFM to SCFM) |
| 60 | 80 | 4.969 | 496.9 (CFM to SCFM) |
| 60 | 90 | 4.878 | 487.8 (CFM to SCFM) |
| 60 | 100 | 4.791 | 479.1 (CFM to SCFM) |
| 70 | 60 | 5.851 | 585.1 (CFM to SCFM) |
| 70 | 70 | 5.74 | 574.0 (CFM to SCFM) |
| 70 | 80 | 5.634 | 563.4 (CFM to SCFM) |
| 70 | 90 | 5.531 | 553.1 (CFM to SCFM) |
| 70 | 100 | 5.433 | 543.3 (CFM to SCFM) |
| 80 | 60 | 6.541 | 654.1 (CFM to SCFM) |
| 80 | 70 | 6.418 | 641.8 (CFM to SCFM) |
| 80 | 80 | 6.299 | 629.9 (CFM to SCFM) |
| 80 | 90 | 6.184 | 618.4 (CFM to SCFM) |
| 80 | 100 | 6.074 | 607.4 (CFM to SCFM) |
| 90 | 60 | 7.232 | 723.2 (CFM to SCFM) |
| 90 | 70 | 7.096 | 709.6 (CFM to SCFM) |
| 90 | 80 | 6.964 | 696.4 (CFM to SCFM) |
| 90 | 90 | 6.838 | 683.8 (CFM to SCFM) |
| 90 | 100 | 6.715 | 671.5 (CFM to SCFM) |
| 100 | 60 | 7.923 | 792.3 (CFM to SCFM) |
| 100 | 70 | 7.773 | 777.3 (CFM to SCFM) |
| 100 | 80 | 7.629 | 762.9 (CFM to SCFM) |
| 100 | 90 | 7.491 | 749.1 (CFM to SCFM) |
| 100 | 100 | 7.357 | 735.7 (CFM to SCFM) |
1 scfm ≈ 1.1199 cfm
1 scfm ≈ 0.8478 m3/min
Special unit conversions:
1 l/min 0.0353 cfm
1 l/min ≈ 0.0299 scfm
1 l/s ≈ 2.1189 cfm
1 l/s ≈ 1.7992 scfm
CFM: only tells the volume flow rate, regardless of the thinness and density of the air
SCFM: has been corrected for environmental differences, easy to compare between different machines and countries
ACFM (actual CFM): the flow rate in the actual use of the environment, closer to the real working performance.
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