# Gas Converter (Nm³, scf, kg, Liquid)

URL: https://hifreetools.com/gas/convert

> Pick the gas, enter the amount in the unit you have — Nm³, Sm³, scf, kg, lb or mol — and see every other unit at once. Choose per hour or per minute to convert flow rates such as SCFM to Nm³/h. The Liquid to gas tab turns litres of liquid nitrogen, oxygen, argon, LNG or CO₂ into kilograms and gas volume using a real-fluid density.

## Quick answer

To convert a gas volume to mass, divide by the molar volume and multiply by the molar mass: 1 Nm³ (0 °C, 1 atm) is 44.615 mol, so 1 Nm³ of nitrogen weighs 1.2498 kg and 1 kg of nitrogen is 0.8001 Nm³. Standard volumes change with the reference temperature: the same gas is 1.055 times larger in Sm³ (15 °C) than in Nm³ (0 °C), and 100 SCFM (60 °F) equals 160.75 Nm³/h.

## Formula

- n = P·V / (R·T) mass = n × M V₂ = V₁ × (T₂ / T₁) × (P₁ / P₂)

## Examples

- 100 Nm³ of nitrogen in kilograms: Nitrogen, 100 Nm³ (0 °C, 1 atm) → 4,461.5 mol = 124.98 kg (275.54 lb)
- A flow rate: 100 SCFM to Nm³/h: Any gas, 100 scf (60 °F), per minute → 160.75 Nm³/h
- 1 kg of carbon dioxide as gas: Carbon dioxide, 1 kg → 0.5093 Nm³ = 0.5373 Sm³ = 19.01 scf (60 °F)
- 100 litres of liquid nitrogen to gas: Liquid nitrogen at 77 K (−196 °C), 1 atm, 100 L → 80.77 kg = 64.63 Nm³ (expansion ratio about 1 : 682 at 15 °C)

## FAQ

**What is the difference between Nm³, Sm³ and scf?**
All three are volumes of gas expressed at agreed reference conditions so amounts can be compared. Nm³ (normal cubic metre) uses 0 °C and 1 atm, Sm³ (standard cubic metre) usually 15 °C and 1 atm as in ISO 13443, and scf (standard cubic foot) 60 °F (industry) or 70 °F (CGA, industrial gases) at 1 atm. The same amount of gas is 1.0549 Sm³ for every Nm³.

**How do I convert SCFM to Nm³/h?**
Choose scf (60 °F) as the unit and Per minute as the rate, then enter the SCFM; every line shows the per-minute and the per-hour value, so the Nm³ line gives Nm³/h directly. As a rule, Nm³/h = SCFM × 1.6075 on the 60 °F basis, or × 1.5771 on the 70 °F (CGA) basis.

**How many kg is 1 Nm³ of nitrogen?**
1.2498 kg at 0 °C and 1 atm (ideal-gas reference). Conversely, 1 kg of nitrogen is 0.8001 Nm³ or 0.844 Sm³ at 15 °C.

**How much gas does 1 litre of liquid nitrogen make?**
About 0.65 Nm³, or 682 litres at 15 °C and 1 atm. The calculator uses the liquid density at the storage condition you set (807.7 kg/m³ at −196 °C by default), so the ratio follows the actual liquid.

**Why does the gas matter for some conversions and not others?**
Volume to volume (Nm³ to scf) depends only on temperature and pressure, so every gas gives the same answer. Volume to mass needs the gas's molar mass, which is why 1 Nm³ of hydrogen weighs 0.09 kg and 1 Nm³ of argon 1.78 kg.

**Is my data uploaded?**
No. The conversion runs in your browser. The liquid tab downloads the property engine once (about 9 MB) and then works offline.


## Sources

- [BIPM — The International System of Units (SI Brochure)](https://www.bipm.org/en/publications/si-brochure)
- [ISO 13443 — Natural gas: standard reference conditions (15 °C, 101.325 kPa)](https://www.iso.org/standard/20461.html)
- [Compressed Gas Association (CGA) — industrial gas standards](https://www.cganet.com/)
- [CoolProp 8.0.0 — open-source thermophysical property library (Bell et al.)](https://coolprop.org/)
- [NIST Chemistry WebBook — Thermophysical Properties of Fluid Systems](https://webbook.nist.gov/chemistry/fluid/)

Runs in the browser; nothing is uploaded. Cite as: HIFreeTools, "Gas Converter (Nm³, scf, kg, Liquid)", https://hifreetools.com/gas/convert