Gas Flow Conversion: Actual to Nm³/h, Sm³/h and SCFM
Convert gas flow at line conditions to normal, standard and US standard units for several lines at once, with pressure, temperature and compressibility.
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- Calculator sheet with a worked example
- How to Use sheet with steps
- 40 built in formulas, no macros
- Yellow input cells, grey results
- Calculation sign off block
- Excel, Google Sheets and LibreOffice
Worked Example
These are the results of the example already filled in the workbook. Replace the yellow cells with your own data.
Conversions
| Line | Actual flow (m³/h) | Pressure (bar g) | Temp. (°C) | Z | Nm³/h (0 °C) | Sm³/h (15 °C) | SCFM (60 °F) | ACFM | Remarks |
|---|---|---|---|---|---|---|---|---|---|
| Compressor discharge | 500.0 | 6.00 | 40.0 | 1.000 | 3,018.7 | 3,184.5 | 1,877.9 | 294.3 | |
| Fuel gas header | 1,200.0 | 3.50 | 25.0 | 0.990 | 4,946.4 | 5,218.0 | 3,077.1 | 706.3 | |
| Nitrogen line | 80.0 | 8.00 | 20.0 | 1.000 | 663.1 | 699.5 | 412.5 | 47.1 |
About this Calculator
Gas flows are quoted in many units and reference conditions, and mixing them is a common source of sizing errors. This sheet converts actual flow to the main reference bases side by side.
Basis: Ideal gas relation with compressibility: Q_ref = Q × (P_abs ÷ P_ref) × (T_ref ÷ T) × (Z_ref ÷ Z), Z_ref taken as 1. Normal 0 °C, 1.01325 bar a; standard 15 °C, 1.01325 bar a; US standard 60 °F, 14.696 psia.
How to use
- Enter actual flow, line pressure (gauge), temperature and Z for each line.
- Adjust atmospheric pressure for site altitude if needed.
- Read Nm³/h, Sm³/h, SCFM and ACFM.
Formulas used
- Nm³/h = Q × (P + Patm) ÷ 1.01325 × 273.15 ÷ T(K) ÷ Z.
- Sm³/h = Nm³/h × 288.15 ÷ 273.15.
- SCFM = Nm³/h × 288.706 ÷ 273.15 × 0.588578.
Related tools
Frequently Asked Questions
Is Nm³/h the same as Sm³/h?
No. Normal usually means 0 °C and standard 15 °C; the difference is about 5.5 %.
Why does SCFM use 60 °F?
It is the common US standard; some industries use 68 °F, so check the basis.
When is Z needed?
At higher pressures or for real gases; at low pressure Z ≈ 1.
Learn more on the blog
Types of flow meters
A practical guide on instrumentationblog.in that explains the engineering behind this workbook.
Read Full Article