Convert a dry-air flow stated at 60°F and 14.7 psia into actual volume at 100°F and 100 psia. Both compressibility factors are assumed to be 1. Always state the reference conditions when using SCFM.
1. Calculator Inputs
Select the units below before entering the numbers. These are fixed benchmark inputs for checking the calculator.
| Calculator field | Value | Unit / setting |
|---|---|---|
| Known flow basis | Standard / normal volume | |
| Known flow rate | 100 | Reference ft³/min |
| Gas / mixture | Dry air | MW = 28.965 g/mol |
| Operating pressure | 100 | psia |
| Operating temperature | 100 | °F |
| Operating compressibility factor, Z | 1 | |
| Reference conditions | 60°F, 14.7 psia | |
| Reference compressibility factor, Z | 1 |
2. Step-by-step Math
Use absolute temperature and pressure
Tref = 60 + 459.67 = 519.67 °R Tactual = 100 + 459.67 = 559.67 °R Pref = 14.7 psia; Pactual = 100 psia
The operating pressure is absolute, not gauge. Atmospheric pressure is not added when psia is selected.
Apply conservation of mass
Qactual = Qref × (Pref/Pactual) × (Tactual/Tref) × (Zactual/Zref) Qactual = 100 × (14.7/100) × (559.67/519.67) × (1/1) Qactual ≈ 15.8 ACFM
Higher pressure reduces the actual volume occupied by the same mass. The temperature rise partly offsets that reduction.
Check density and mass flow independently
ρref = Pref MW / (Zref R Tref) Pref ≈ 101,000 Pa MW = 0.028965 kg/mol; R = 8.31446261815324 J/(mol·K) Tref ≈ 289 K ρref = 1.222983293 kg/m³ Qref = 100 × 0.028316846592 / 60 = 0.04719474432 m³/s ṁ = ρref Qref = 0.057718383833 kg/s ṁ = 458.090116904 lb/h
At operating conditions, density is 7.725005686 kg/m³. Dividing mass flow by that density gives 0.007471629949 m³/s, the same 15.831487290 ACFM.
3. Compare Your Answers
Keep full precision during the calculation. The calculator may display fewer digits; compare answers rounded to three significant figures; retain unrounded intermediate values.
| Result | Expected answer | Your answer |
|---|---|---|
| Actual volume flow | 15.8 ACFM | __________ |
| Reference flow | 100 reference ft³/min | __________ |
| Mass flow | 458 lb/h | __________ |
| Operating density | 7.73 kg/m³ | __________ |
Second check
Switch the known flow basis to Actual volume at operating conditions, choose Actual ft³/min, and enter 15.831487290. With all conditions unchanged, reference flow returns to 100 ft³/min. At equal operating and reference conditions with equal Z, the two volume flows must be equal.
4. Assumptions and Method
Dry-air molecular weight is fixed at 28.965 g/mol. Z = 1 is an explicit ideal-gas assumption, not a property prediction. This conversion does not calculate pressure loss, choking, condensation or changing composition.
Equation definitions and implementation: Gas-Flow Conversion Calculator. See also calculation methodology and other worked examples.