How to convert hydrogen kg to Nm³ at 0°C and 1 atm
For pure hydrogen at 0°C and 1 atm, use 11.126 Nm³ per kg. The reciprocal is about 0.08988 kg per Nm³. This is an amount conversion using NIST real-gas data; a 1 bar ideal-gas calculation uses a different reference basis.
State what Nm³ means before using a factor
A kilogram measures hydrogen mass. A normal cubic metre measures volume after a reference temperature and pressure have been chosen. The symbol Nm³ alone does not tell every reader which reference conditions were used. In this guide, the basis is pure hydrogen at 0°C and 1 atm absolute pressure.
NIST's hydrogen property table gives a specific volume of 11.1256352 m³/kg at 0°C and 1 atm, rounded here to 11.126 Nm³/kg. IUPAC's standard conditions for gases use 0°C and 100 kPa, or 1 bar. That pressure differs from 1 atm, which is 101.325 kPa. Keep the IUPAC 1 bar convention and an ideal-gas calculation separate from this NIST real-gas value.
Sources
NIST Chemistry WebBook, SRD 69
Isobaric Properties for Hydrogen
Fluid Data at P = 1.0000 atm; 0°C row, Volume 11.1256352 m³/kg and Density 0.0898825082 kg/m³
Last confirmed: 2026-10-21
IUPAC Gold Book
Standard conditions for gases (S05910)
Term definition: 273.15 K and 100,000 Pa; notes the former 1 atm standard pressure as 101,325 Pa
Last confirmed: 2026-10-21
Multiply or divide by the same specific volume
To convert mass to reference volume, multiply kilograms by 11.126. To convert the same reference volume back to mass, divide by 11.126. The factor is tied to the stated gas and conditions, so retain those details when copying a result into a specification or comparison.
The examples below are H2Prism calculations at the stated basis. They do not describe a measured batch or a project's production capacity.
H₂ volume (Nm³) = H₂ mass (kg) × 11.126 Nm³/kg; H₂ mass (kg) = H₂ volume (Nm³) ÷ 11.126 Nm³/kg
| Given amount | Converted amount | Calculation |
|---|---|---|
| 1 kg | 11.126 Nm³ | 1 × 11.126 |
| 10 kg | 111.26 Nm³ | 10 × 11.126 |
| 100 Nm³ | 8.99 kg | 100 ÷ 11.126 |
H2Prism calculations using NIST's rounded pure-hydrogen specific volume. The reference conditions are part of each result.
Sources
NIST Chemistry WebBook, SRD 69
Isobaric Properties for Hydrogen
Fluid Data at P = 1.0000 atm; 0°C row, Volume 11.1256352 m³/kg and Density 0.0898825082 kg/m³
Last confirmed: 2026-10-21
Keep an amount separate from a flow rate
kg and Nm³ are amounts; kg/h and Nm³/h are rates. The same factor converts a matched pair of rates: 1 kg/h corresponds to 11.126 Nm³/h on this basis. The hour remains in both units. A mass amount cannot be compared directly with an hourly flow unless an operating time is also known.
Reference volume is also different from the physical volume in a pipe or vessel. Actual gas volume depends on operating temperature, absolute pressure and composition. Use properties for those actual conditions when sizing equipment; do not use the normal-volume factor as a pipe or storage calculation.
Check the amount conversion in the existing tool
Open the Hydrogen Converter's Amount & energy tab, enter a value and compare kg with Nm³. The tool labels its Nm³ basis as 0°C, 1 atm and real gas. For hourly production or consumption, use the separate Flow & capacity tab so the time unit stays attached to the result.
Common questions
How many Nm³ are in 1 kg of hydrogen?
About 11.126 Nm³ at 0°C and 1 atm for pure real-gas hydrogen, using the NIST specific volume adopted by the converter.
Is 11.126 the same as an ideal-gas value at 1 bar?
No. The converter's factor is real-gas hydrogen at 1 atm. IUPAC standard gas conditions use 1 bar at 0°C, so keep the reference pressure and gas model explicit.
What is the difference between kg and kg/h?
kg is a mass amount; kg/h is mass per hour. Convert matching amount units or matching flow units, and include operating time when moving between them.