What is the difference between Sm³ and Nm³?

Both are based on a pressure of 1.01325 bar; Sm³ is based on 15 °C, Nm³ is according to 0 °C. 1 Nm³ ≈ 1.055 Sm³. Natural gas billing in Turkey is done via Sm³.

When is the Z-factor important?

At low pressure (up to a few bar) Z ≈ 1 can be taken. For natural gas it is about 0.99 at 4 bar and about 0.95 at 20 bar; it should be taken into account in high pressure measurements.

Natural Gas Sm³ Calculation – Meter Pressure and Temperature Correction

Gas meters measure gas by its actual volume at the pressure and temperature. Billing and fuel consumption comparisons are made in standard cubic metres (Sm³, 15 °C and 1.01325 bar) or normal cubic metres (Nm³, 0 °C and 1.01325 bar). This tool performs the conversion by adjusting for pressure, temperature and compressibility.

Formula

V(Sm³) = V(real) · (p / 1.01325) · (288.15 / T) / Z

p: absolute gas pressure (bar), T: gas temperature (K), Z: compressibility factor. Enter local atmospheric pressure from advanced settings at high altitudes.

Example

100 m³/h of natural gas measured at 300 mbar(g) and 15 °C corresponds to 129.6 Sm³/h (122.9 Nm³/h). 100 m³/h measured at 4 bar(g) and 10 °C is approximately 503.5 Sm³/h .

You can calculate your fuel needs with the boiler fuel consumption tool. To evaluate your steam system as a whole, you can take a look at our steam boiler guide and get a free quote for your project.

Natural Gas Sm³ / Nm³ Conversion Calculation

Formula

Example

Frequently Asked Questions