Flow Measurement · Glossary

What is Standard Volume Flow?

Symbol: Nm³/h, Sm³/h, SCFMgas volume at reference conditionsFlow Measurement

Standard volume flow is gas flow converted to a reference pressure and temperature, so it represents a fixed amount of gas.

Standard Volume Flow Explained

A cubic metre of gas at 10 bar holds about ten times more gas than at atmospheric pressure. Converting to reference conditions makes gas flows comparable, like a mass flow expressed in volume units.

Reference conditions differ. Always state them: normal (often 0 °C, 1.01325 bar a), standard (often 15 °C, 1.01325 bar a) or US standard (60 °F, 14.696 psia).

Standard Volume Flow Formula

Q_n = Q × (p ÷ p_n) × (T_n ÷ T) × (Z_n ÷ Z)

Q	actual flow at line conditions
p, T	line absolute pressure and temperature (K)
p_n, T_n	reference conditions
Z	compressibility factor

Example: 100 m³/h at 5 bar g and 30 °C (Z = 1) is 100 × (6.013 ÷ 1.013) × (273.15 ÷ 303.15) ≈ 535 Nm³/h.

Calculators for Standard Volume Flow

CalculatorGas Flow Conversion CalculatorFree online calculator with formula and worked example.CalculatorGas Density CalculatorFree online calculator with formula and worked example.CalculatorGas Flow Pressure and Temperature Compensation CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Standard Volume Flow?

Standard volume flow is gas flow converted to a reference pressure and temperature, so it represents a fixed amount of gas.

Is Nm³ the same as Sm³?

No. They use different reference temperatures in most conventions, which gives about a 5 % difference. Check which one the specification uses.

Why use absolute pressure?

Gas laws work with absolute pressure. Using gauge pressure gives large errors at low pressures.

Learn more on the blog

Types of flow meters

A practical guide on instrumentationblog.in with more detail on standard volume flow and how it is applied on real plants.

Read Full Article

More Flow Measurement Terms

Flow termWeirA weir is a barrier with a notch in an open channel; the height of water above the crest gives the flow rate.Flow termRotameterA rotameter is a variable area flow meter where a float rises in a tapered tube until drag balances its…Flow termVolumetric Flow RateVolumetric flow rate is the volume of fluid passing a point per unit time, equal to pipe area times…Flow termReynolds NumberReynolds number is the ratio of inertial to viscous forces in a flowing fluid. It shows whether pipe flow…Flow termLaminar FlowLaminar flow is smooth flow in parallel layers with no mixing between them, found at low Reynolds numbers.Flow termTurbulent FlowTurbulent flow is chaotic flow with eddies and mixing across the pipe, found at high Reynolds numbers.

All flow measurement terms · Full glossary A to Z