Hydrogen unit converter
Convert hydrogen between mass, moles, volume (at real-world conditions) and energy (LHV or HHV), with avoided CO2 versus a grey-hydrogen baseline.
Ionect hydrogen unit converterThe Ionect hydrogen unit converter interconverts hydrogen mass, moles, volume (at normal, standard, US standard, compressed, and liquid conditions) and energy on a Lower or Higher Heating Value basis, and estimates the CO2 avoided when this hydrogen displaces grey hydrogen from steam methane reforming.
Efficiency and cost figures can differ by roughly 18 percent for hydrogen depending on the basis, so always state which one is used. Every energy result here is labelled with its basis.
Mass and moles
Volume
Energy (LHV basis)
Fuel-equivalent context (LHV)
Climate context (avoided CO₂ vs grey H₂)
Indicative production requirements
Indicative only. Use the Green Hydrogen Calculator for a proper production estimate.
Definitions and conventions
- LHV (NCV)
- Lower Heating Value (Net Calorific Value): the usable heat from combustion when the water produced stays as vapour. For hydrogen, 119.96 MJ/kg (33.33 kWh/kg). The standard basis for engine and fuel-cell efficiency and most energy accounting.
- HHV (GCV)
- Higher Heating Value (Gross Calorific Value): includes the extra heat recovered if the water vapour condenses. For hydrogen, 141.88 MJ/kg (39.41 kWh/kg), about 18 percent higher than LHV. Used in some North American and gas-industry conventions.
- LHV vs HHV
- Efficiency and cost figures can differ by roughly 18 percent for hydrogen depending on the basis, so always state which one is used. Every energy result here is labelled with its basis.
- Nm³
- Normal cubic metre: gas volume at 0 degrees C and 1 atm (101.325 kPa). The common European reference. 1 kg of hydrogen is 11.126 Nm3.
- Sm³
- Standard cubic metre: gas volume at 15 degrees C and 1 atm. About 5 percent larger than an Nm3 for the same mass because the gas is warmer. 1 kg of hydrogen is about 11.74 Sm3.
- scf
- Standard cubic foot: the US convention, at 60 degrees F and 1 atm. 1 kg of hydrogen is about 423 scf. Mixing Nm3, Sm3, and scf without stating conditions is a frequent source of error.
- Compressed and liquid
- Hydrogen does not behave as an ideal gas at high pressure. The 350 and 700 bar volumes use real-gas behaviour and depend on temperature, so they are approximate. Liquid hydrogen is at about -253 degrees C with a density near 70.85 kg/m3.
- Grey-H₂ baseline
- The CO2 emitted per kg of hydrogen made by unabated steam methane reforming, the incumbent route. Used to estimate the CO2 avoided when low-carbon hydrogen displaces it. Direct process emissions are about 9, rising to roughly 10 to 12 with upstream gas emissions included.
Conversions use standard physical constants. Compressed and liquid hydrogen volumes are real-gas approximations that depend on temperature. See also the energy unit converter, CO₂ emissions calculator, green hydrogen calculator, e-fuel cost estimator and the green hydrogen Knowledge Hub.
Frequently asked questions
How many Nm³ is 1 kg of hydrogen?
11.126 Nm³ at 0°C and 1 atm.
How much energy is in 1 kg of hydrogen?
33.33 kWh LHV, or 39.41 kWh HHV.
What is the difference between LHV and HHV for hydrogen?
HHV is about 18 percent higher because it counts the heat from condensing the water vapour produced.
What is the difference between Nm³, Sm³, and scf?
They are gas volumes at different reference conditions: 0°C/1 atm, 15°C/1 atm, and 60°F/1 atm respectively.
How much does 1 kg of hydrogen take as a volume at 700 bar?
About 25 litres, real-gas, depending on temperature.
What is the density of liquid hydrogen?
About 70.85 kg/m³ at −253°C, so 1 kg is about 14.1 litres.
How much CO2 does 1 kg of green hydrogen avoid versus grey?
About 9 to 12 kg, depending on the grey baseline assumed.
How many moles in 1 kg of hydrogen?
About 496 mol, since the molar mass of H2 is 2.016 g/mol.