In earlier posts, we considered gas meter types and the difference between volumetric and mass flow rates; here, we show the gas mass flow rate units of measure.

Gas Mass Flow Measurement

gas mass flow rate units of measure
The Sage Thermal Mass Flow Meter calibration is the foundation for the award-winning meter to achieve accurate gas mass flow measurement.

Flow measurement is the measure of bulk fluid movement and determined through:

    • Positive displacement meters, which collect a fixed volume of fluid, release and refill the fluid, then tally the times the amount fill to quantify flow.
    • Flow measurement devices which rely on the strength produced by the flowing stream, as it prevails over a known constriction, and indirectly calculates flow.
    • Flow may also be determined by measuring the velocity of fluid over a known area.

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Units of Measure

Both gas and liquid flow can be expressed in volumetric or mass flow rates, and the quantities can be converted between one another if the substance’s density is known. The density for a liquid is mostly independent of the liquid circumstances, while, for gas, the density is contingent on pressure, temperature, and to a smaller degree, the gas composition.

When gases or liquids transport for sale, the flow rate is often conveyed by energy flow, such as BTU/day or GJ/hour. The energy flow rate equals:

Volume flow rate X energy content/unit volume


Mass flow rate X the energy content/unit mass

While flow meters calculate the volume flow rate or mass flow rate, a flow computer determines the energy flow rate.

The volumetric flow rate is usually denoted by the symbol, and the symbol  is used for the mass flow rate.

Flow Rate

Gases are compressible and change volume when:

    • Under pressure
    • Heated
    • Cooled

In other words, a volume of gas at established pressure and temperature conditions does not equal the same gas under different pressure or temperature conditions. Because of this, meter flow rates are referred to “actual” and “standard” or “base” flow rates with units such as:

    • acm/h (actual cubic meters/hour)
    • kscm/h (kilo standard cubic meters/hour)
    • LFM (linear feet/minute)
    • MSCFD (million standard cubic feet/day)

Gas mass flow rate can be directly measured, independent of pressure and temperature effects, with thermal mass flow meters, Coriolis mass flow meters, or mass flow controllers.

For a review of mass, volume and density, this video may interest you.


One thought on “Units of Measure: Gas Mass Flow

  1. Avatar
    Yucel Copur says:


    We are looking a company which can establish a Natural Gas Flowmeter Calibration Laboratory.

    Working fluid will be Natural Gas and the pressure will be over 4 bar and up to 50 Bar.

    Can you help us?

    Best Regards

    Yücel Çopur
    Mechanical Engineer
    Project Manager

    Mevlana Bulvarı Yelken Plaza 8.Kat No:139/28
    Balgat / Çankaya / ANKARA / TURKEY
    Phone : +90 312 318 07 07 – 418 28 87 – 425 79 66
    Fax : +90 312 417 66 36
    Mobile : +90 535 570 55 15

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