Gas quantities

Gas Unit Converter & Helium Calculator

Convert quantities with the gas, pressure basis and reference conditions clearly stated.

JavaScript is required for calculations. The method notes and gas quantities guide remain available below.

Choose a calculation Liquid helium Gas mass and volume Helium in cylinders and bundles Mass and pressure units

Liquid helium quantity

Approximate density: 0.12474 kg/L at −268.93 °C and 1.013 bar absolute. Not the water capacity of a tank.

Liquid helium amountInput unit

Gas-equivalent reference conditions

This changes the volume equivalent, never the mass. The label “standard” alone is not a complete specification.

Temperature and absolute pressureResult volume unit

Use 20.5 or 20,5 for a decimal; no thousands separators. For a three-place decimal such as 1.508, enter 1.5080.

Know what the number represents

Three different volumes

Liquid litres describe liquid helium. Water capacity describes the inside of a vessel. Gas-equivalent volume describes a quantity at a stated temperature and absolute pressure. They are not interchangeable.

Read the guide to litres, kilograms, Nm³ and SCF.

Methods and boundaries

Ordinary gas equivalents use the ideal-gas relation with Z = 1 and molar masses from CIAAW; argon assumes atmospheric isotopic composition. Liquid helium uses the state-specific density in Air Liquide's gas encyclopedia.

This tool does not determine safe filling limits, withdrawable gas, purity or isotope enrichment. For an enquiry, confirm packaging, quality requirements and the delivery basis.