Standard to Actual Gas Flow Calculator
Gas volume changes with pressure and temperature. Convert a standard or normal flow to the actual flow at line conditions, or the reverse, for meter sizing and reporting.
- Factor = (Pref ÷ P) × (T ÷ Tref) × Z = (1.0132 ÷ 8) × (303.15 ÷ 273.15) × 1 = 0.14057
- Actual = standard × factor = 140.57
Gas Flow Conversion
Pressures are absolute and temperatures in kelvin. Zref is taken as 1, which is accurate for air and most gases at reference conditions.
Worked example
1000 Nm³/h of air at 8 bar(a) and 30 °C is 1000 × (1.01325 ÷ 8) × (303.15 ÷ 273.15) = 140.6 m³/h actual.
Frequently Asked Questions
What is the difference between Nm³ and Sm³?
Normal cubic metres are referred to 0 °C and 1.01325 bar; standard cubic metres usually to 15 °C (or 20 °C) and 1.01325 bar. They differ by about 5.5 %.
Why must pressure be absolute?
Gas laws use absolute pressure. Add atmospheric pressure (about 1.013 bar) to gauge readings.
What is SCFM?
Standard cubic feet per minute, usually at 60 °F and 14.696 psia in the oil and gas industry.
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