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SimuPipe

Gas Flow Converter

Convert gas flow between actual, normal, standard, and mass flow units. On the input side a unit is just a scale and the conditions carry the state: enter SCFM as ft³/min with the US standard preset, or Nm³/h as m³/h with the Normal (DIN 1343) preset — the reference conditions are what most conversions get wrong.

Flow Input
All Conversions

Actual — at line conditions

m³/h (actual)
13.5705
m³/min (actual)
0.226175
L/min (actual)
226.175
ACFM
7.98731

Normal — 0 °C / 101.325 kPa (DIN 1343)

Nm³/h
100
Nm³/min
1.66667
Nl/min
1,666.67

Standard

Sm³/h
105.491
SCFM
62.0899
SCFH
3,725.4

Mass flow

kg/h
129.223
kg/s
0.0358953
lb/h
284.888
lb/min
4.74813
How the Conversion Works

Converting a gas flow from one reference condition to another is an ideal-gas volume correction. The same mass of gas occupies a different volume at each temperature and pressure:

Qref=Qact⋅PactPref⋅TrefTactQ_{ref} = Q_{act} \cdot \frac{P_{act}}{P_{ref}} \cdot \frac{T_{ref}}{T_{act}}

Mass flow is the condition-independent quantity, so this converter works through it: the volumetric flow is multiplied by the gas density at its own reference condition, and the result is re-expanded at every other condition. Density follows from the ideal gas law with M the molecular mass:

ρ=P MR Tm˙=Q⋅ρ\rho = \frac{P \, M}{R \, T} \qquad \dot{m} = Q \cdot \rho

All pressures are absolute. The converter assumes ideal-gas behaviour (Z = 1), which is accurate for reference-condition conversions and low-pressure lines; at high line pressures the actual-flow figures deviate by the gas's compressibility factor.

Reference Conditions Compared

"Standard" conditions are not standardised — the same SCFM label can mean different reference states depending on the industry. Always check which definition your instrument, datasheet, or contract uses.

NameTP (abs)Typical use
Normal (DIN 1343)0 °C101.325 kPaNm³/h, Nl/min — European process and instrumentation
Standard (ISO 13443)15 °C101.325 kPaSm³/h — natural gas, international
Standard (US)60 °F14.696 psiaSCFM, SCFH, MMSCFD — US oil and gas
US pipeline (AGA)60 °F14.73 psiaGas measurement contract base (state bases range 14.65–15.025 psia)
ISO 1217 / ISO 635820 °C100 kPaCompressor ratings (CAGI, dry air) and pneumatics ANR
NTP20 °C101.325 kPaLaboratory and ventilation contexts

Frequently Asked Questions

What is the difference between actual, normal, and standard flow?
Actual flow (ACFM, actual m³/h) is the volume the gas really occupies at line temperature and pressure. Normal flow (Nm³/h) re-expresses the same mass flow at 0 °C and 101.325 kPa (DIN 1343). Standard flow (Sm³/h, SCFM) does the same at a "standard" state, commonly 15 °C / 101.325 kPa (ISO 13443) or 60 °F / 14.696 psia in the US. The mass flow is identical in every case — only the reference volume changes. Compressed air example: 100 Nm³/h of air at 7 bar(g) and 20 °C occupies only about 13.6 m³/h of actual pipe volume.
How do I enter SCFM, ACFM, or Nm³/h in this converter?
Pick the plain scale under From unit and let the input conditions carry the reference state. For SCFM, choose ft³/min (CFM) and set the Standard preset to 60 °F / 14.696 psia (US gas industry). For Nm³/h, choose m³/h with the Normal (DIN 1343) preset — and for Sm³/h, the same with the ISO 13443 preset. For ACFM or any other actual flow, choose ft³/min (or m³/h) and type your line temperature and pressure into the input-conditions fields; the preset then shows Custom, which is correct — actual flow is referenced to your line state, not to a standard.
How do I convert SCFM to Nm³/h?
Multiply by the cubic-feet-to-cubic-metres factor (0.02832) and correct for the temperature difference between the two reference states. On the 60 °F US basis, 1 SCFM = 1.699 standard m³/h, and correcting 15.6 °C down to 0 °C gives about 1.61 Nm³/h. On a 68 °F (20 °C) basis the factor is about 1.58. The spread between those numbers is exactly why you should state the reference conditions rather than quote a bare conversion factor.
Why does "standard" mean different things in different industries?
The reference states grew up independently: the international natural gas industry settled on 15 °C / 101.325 kPa (ISO 13443), the US gas industry on 60 °F / 14.696 psia, compressor manufacturers on 20 °C / 100 kPa dry air (ISO 1217, used by CAGI), and laboratories on 20 °C or 25 °C variants. The differences are only a few percent, but on a compressor purchase or a billing meter a few percent matters. This converter makes the choice explicit instead of hiding it.
How do I convert Nm³/h to kg/h?
Multiply by the gas density at normal conditions: density = P·M / (R·T) with P = 101,325 Pa, T = 273.15 K, M the molecular mass. For air (M = 28.964 g/mol) that gives 1.292 kg/m³, so 100 Nm³/h of air is about 129 kg/h. For methane (M = 16.043 g/mol) it is 0.716 kg/m³, so 100 Nm³/h is about 72 kg/h.
Does this converter account for real-gas compressibility?
No — it uses the ideal gas law (Z = 1). That is accurate for converting between reference conditions, which are all near atmospheric, and for actual-flow conversion at modest line pressures. At high line pressures the actual volume deviates by the compressibility factor Z (a few percent for air at tens of bar, more for CO₂ or heavy hydrocarbons near their critical points). SimuPipe's pipe network simulator applies a Peng-Robinson equation of state for those cases.
Do SCFM ratings include humidity?
Some definitions do. ISO 1217 / CAGI compressor ratings reference dry air (0% relative humidity), while the older ASME "standard air" definition used 68 °F, 14.696 psia and 36% relative humidity. This converter assumes dry gas. The water-vapour correction is small at typical intake conditions but is worth checking when comparing compressor capacity claims.

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