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Refrigerants & gases

Helium · He

Helium (He, CAS 7440-59-7) is an industrial and utility gas; this page gives its density, heat capacity and viscosity from 1 to 300 bar and -20 to 100 °C.

Values are computed from CoolProp==6.6.0 - reference Helmholtz equation of state for Helium (single-phase density, isobaric heat capacity and dynamic viscosity) and tabulated over 1–300 bar (absolute) and -20–100 °C.

Also known as
He, helium-4, GHe, gaseous helium
CAS number
7440-59-7
Tabulated range
1–300 bar · -20–100 °C
Identity
Molar mass
4.003g/mol
Critical temperature
-267.95°C
Critical pressure
2.276bar
Normal boiling point
-268.93°C

NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems. NIST Chemistry WebBook, SRD 69, Thermophysical Properties of Fluid Systems, helium (He, CAS 7440-59-7): molar mass, critical point and normal boiling point. https://webbook.nist.gov/cgi/fluid.cgi?ID=C7440597&Action=Page

At 25 °C
reference snapshot
Density · 1 bar
0.1614kg/m³
Density · 300 bar
42.54kg/m³
Heat capacity · 1 bar
5193J/kg·K
Viscosity · 1 bar
19.846uPa.s
Compressibility · 300 bar
1.139Z
Explore

Read a value at any pressure and temperature

Set a pressure (bar absolute) and a temperature (°C) to interpolate between the tabulated grid points. The readout and chart never go outside the validated 1–300 bar and -20–100 °C range, and every number is interpolated from the committed table below — nothing is computed from an equation of state in your browser.

Interactive explorer

Values are interpolated between the tabulated grid points below — pressure (bar absolute) and temperature (°C) stay within the validated 1–300 bar and -20–100 °C range and are never extrapolated.

1 bar
25 °C
Density
0.1614 kg/m³
Specific volume
6.196 m³/kg
Compressibility Z
1.0004
Heat capacity
5193 J/kg·K
Viscosity
19.846 uPa.s
Density (kg/m³) vs pressure (bar) for He at 25 °C — Helium.
Full tables

Every tabulated point

Rows are temperature (°C); columns are pressure (bar absolute). Read the cell at the intersection. Density is the single-phase fluid density at that state.

Density — kg/m³
°C \ bar125102050100200300
-200.19010.37990.94811.89093.76049.245818.0034.2148.94
00.17610.35210.87891.75323.48828.587516.7531.9645.87
150.16700.33380.83331.66243.30868.152315.9330.4643.81
250.16140.32260.80541.60703.19887.885915.4229.5342.54
500.14890.29770.74321.48322.95377.290214.2827.4539.66
750.13820.27630.69001.37722.74356.778313.3025.6437.14
1000.12900.25780.64391.28532.56126.333512.4424.0534.92
Isobaric heat capacity — J/kg·K
°C \ bar125102050100200300
-20519351935194519451955198520352095213
0519351935194519451955197519952045207
15519351935193519451945196519852015203
25519351935193519451945195519751995200
50519351935193519351935194519451955195
75519351935193519351935193519351925191
100519351935193519351935192519151905188
Dynamic viscosity — uPa.s
°C \ bar125102050100200300
-2017.75317.75817.77417.80017.85118.00118.23718.66619.050
018.69418.69918.71218.73518.77918.90719.11019.48119.814
1519.38819.39219.40419.42419.46219.57519.75320.08120.377
2519.84619.84919.86019.87719.91220.01420.17720.47620.748
5020.97120.97420.98421.00021.03221.12521.27421.55121.803
7522.07322.07622.08522.10022.13022.21722.35622.61522.854
10023.15423.15623.16523.17923.20623.28823.41823.66323.889
Typical values

Helium density at pressure (25 °C)

At 100 bar and 25 °C, helium density is about 15.4 kg/m³. At 200 bar and 25 °C, helium density is about 29.5 kg/m³. At 300 bar and 25 °C, helium density is about 42.5 kg/m³.

Sources

Where the numbers come from

Every value on this page is computed by a deterministic equation of state — none is entered by hand. The generating method and the references it is checked against:

  • ▸NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems (REFPROP-derived isothermal tables), helium (CAS 7440-59-7)
  • ▸CoolProp 6.6.0 - reference Helmholtz equation of state for Helium (Ortiz-Vega, Hall, Arp & Lemmon, 2019); dynamic viscosity from the Arp, McCarty & Friend, 1998 model

Model: CoolProp==6.6.0 - reference Helmholtz equation of state for Helium (single-phase density, isobaric heat capacity and dynamic viscosity) · Generated 2026-06-07

The committed data file for this page is published as JSON on GitHub under CC BY 4.0.

Validation

Checked against cited values

The equation of state is cross-checked against independently cited NIST WebBook reference points — a near-ambient and a compressed density, plus the heat-capacity and viscosity columns. The page is published only because every check passes.

Property / pointDensity · 1 bar · 25 °C
Cited reference value0.1614 kg/m3
Model computed0.1614 kg/m3
Error vs reference0.002% (tolerance 1%)

NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems. NIST Chemistry WebBook, SRD 69, Thermophysical Properties of Fluid Systems, helium (He, CAS 7440-59-7), isothermal table at 298.15 K: density at 1 bar = 0.16139 kg/m3. https://webbook.nist.gov/cgi/fluid.cgi?ID=C7440597&Action=Page

Property / pointDensity · 300 bar · 25 °C
Cited reference value42.538 kg/m3
Model computed42.5383 kg/m3
Error vs reference0.001% (tolerance 1%)

NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems. NIST Chemistry WebBook, SRD 69, Thermophysical Properties of Fluid Systems, helium (He, CAS 7440-59-7), isothermal table at 298.15 K: density at 300 bar = 42.538 kg/m3. https://webbook.nist.gov/cgi/fluid.cgi?ID=C7440597&Action=Page

Property / pointIsobaric heat capacity · 1 bar · 25 °C
Cited reference value5193.2 J/kg.K
Model computed5193.2 J/kg.K
Error vs reference0% (tolerance 2%)

NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems. NIST Chemistry WebBook, SRD 69, Thermophysical Properties of Fluid Systems, helium (He, CAS 7440-59-7), isothermal table at 298.15 K: isobaric heat capacity Cp at 1 bar = 5193.2 J/kg.K. https://webbook.nist.gov/cgi/fluid.cgi?ID=C7440597&Action=Page

Property / pointDynamic viscosity · 1 bar · 25 °C
Cited reference value19.846 uPa.s
Model computed19.846 uPa.s
Error vs reference0.002% (tolerance 2%)

NIST Chemistry WebBook, SRD 69 - Thermophysical Properties of Fluid Systems. NIST Chemistry WebBook, SRD 69, Thermophysical Properties of Fluid Systems, helium (He, CAS 7440-59-7), isothermal table at 298.15 K: dynamic viscosity at 1 bar = 19.846 uPa.s. https://webbook.nist.gov/cgi/fluid.cgi?ID=C7440597&Action=Page

Limitations

Before you use these numbers

  • ▸CoolProp reference Helmholtz equation of state (Ortiz-Vega, Hall, Arp & Lemmon, 2019) for helium; dynamic viscosity from the Arp, McCarty & Friend, 1998 model. Single-phase density, isobaric heat capacity and dynamic viscosity, tabulated on a 1-300 bar (absolute) by -20 to 100 degC grid; two-phase, saturation and liquid states are out of scope for this page. The correlation is not extrapolated beyond the tabulated range. Values are for preliminary design; verify against vendor or reference data for critical service.
  • ▸Every tabulated state is single-phase. A grid cell is left blank only where the state at that pressure and temperature would be two-phase or liquid - at or above the saturation pressure at that temperature - and the explorer will not interpolate across such a cell. Because the critical temperature of helium is -267.95 degC, below the -20 degC floor of this grid, every (pressure, temperature) point tabulated here is a supercritical single-phase fluid, so no cell is blank.
  • ▸Values are tabulated only inside the 1–300 bar and -20–100 °C ranges shown; the equation of state is not extrapolated beyond them here.
  • ▸Use for preliminary design; verify for critical service.
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