Liquid Ethylene Density Calculator
This calculator gives you the density of liquid ethylene (C2H4) two ways: enter the storage temperature to get density from the empirical saturation curve, or enter a measured mass and volume for a direct density calculation. Results appear instantly in kg/m3, g/cm3, and lb/ft3.
What is liquid ethylene and why does density matter?
Ethylene (C2H4, also written CH2=CH2) is the simplest alkene and one of the highest-volume industrial chemicals in the world. At atmospheric pressure it is a colorless, flammable gas at room temperature, but it liquefies below its normal boiling point of -103.7 C (-154.7 F). Liquid ethylene is stored and transported under cryogenic conditions, much like liquid natural gas (LNG), typically in insulated tanks aboard specialist ships and railcars. Density is critical for two practical reasons: first, it determines how much mass fits in a given storage volume, which directly affects the economics of transport and inventory management; second, it is needed to convert between volume-based flow measurements and the mass-based contracts that dominate ethylene trading. A 1% error in density translates directly to a 1% error in the mass delivered.
How this calculator works - two methods
The calculator offers two independent methods. The temperature lookup method uses the empirical linear fit rho = 771.35 - 0.456 x T (where T is in Celsius and rho is in kg/m3). This equation is fitted to NIST saturation data for pure liquid C2H4 between the melting point (-169.15 C) and the normal boiling point (-103.74 C) at atmospheric pressure. It is accurate to within roughly 1 kg/m3 across that range, which is sufficient for most engineering purposes. At storage temperatures near -120 C the fit gives about 571 kg/m3, in good agreement with published NIST values. The mass and volume method applies the fundamental definition rho = m / V, which is the most accurate approach when you have direct measurements of both quantities from a calibrated tank or flow meter. Enter your mass and volume in any of the supported units - kilograms, grams, pounds or metric tonnes for mass; litres, millilitres, cubic metres, cubic feet or US gallons for volume - and the calculator converts everything to SI before computing.
Temperature and pressure limits
The temperature lookup is valid only for pure liquid ethylene at or near atmospheric pressure (1.013 bar). Below -169.15 C the substance is a solid; above -103.7 C at 1 atm it is a gas. If you need density at elevated pressures (for example, inside a pressurised storage sphere or during pipeline transport above the saturation curve) you must account for the pressure contribution, which is not trivial near the saturation boundary. At low pressures the Peng-Robinson or Soave-Redlich-Kwong equations of state give reasonable results, but for publication-quality work the reference equation of state by Jahangiri, Jacobsen, Stewart and McCarty (1986) - implemented in NIST REFPROP - is the recommended tool. The critical point of ethylene is at 9.20 C (282.35 K) and 50.41 bar; the liquid becomes indistinguishable from the vapor above this point.
Unit conversions and industrial context
This calculator outputs density in kg/m3, g/cm3, lb/ft3 and lb/gal simultaneously, covering the most common needs in both SI and US customary workflows. At the normal boiling point the liquid density is about 567.9 kg/m3 - roughly half that of water (1000 kg/m3). In practical terms, a 200 m3 cryogenic storage tank holding liquid ethylene at -120 C contains approximately 200 x 571 = 114 200 kg (about 114 tonnes) of product. The specific volume (the reciprocal of density, in m3/kg) is also provided because some process-engineering calculations, especially those involving the compressibility factor and equations of state, use that form directly.
Liquid ethylene density at saturation (1 atm)
| Temperature (°C) | Temperature (K) | Density (kg/m3) | Density (g/cm3) | Density (lb/ft3) |
|---|---|---|---|---|
| -169 | 104.15 | 648 | 0.648 | 40.45 |
| -160 | 113.15 | 634.3 | 0.6343 | 39.60 |
| -150 | 123.15 | 619 | 0.619 | 38.64 |
| -140 | 133.15 | 603.4 | 0.6034 | 37.67 |
| -130 | 143.15 | 587.4 | 0.5874 | 36.67 |
| -120 | 153.15 | 571 | 0.571 | 35.65 |
| -110 | 163.15 | 553.9 | 0.5539 | 34.58 |
| -103.7 | 169.45 | 567.9 | 0.5679 | 35.45 |
Empirical saturation curve data. Values are for pure liquid C2H4 at 1.013 bar. Source: NIST / Jahangiri et al. (1986).
Frequently asked questions
What is the density of liquid ethylene at its boiling point?
At the normal boiling point (-103.74 C, 169.41 K) and 1 atmosphere pressure, liquid ethylene has a density of approximately 567.9 kg/m3 (0.5679 g/cm3 or 35.46 lb/ft3). This is the most commonly cited reference value for cryogenic ethylene storage calculations.
Why does liquid ethylene density decrease as temperature rises?
As temperature increases, the molecules gain thermal kinetic energy and move farther apart on average. For liquid ethylene between -169 C and -104 C, density falls approximately linearly from about 648 kg/m3 near the melting point down to about 568 kg/m3 at the boiling point - a drop of roughly 0.456 kg/m3 per degree Celsius. Very close to the critical point (9.2 C, 50.4 bar) the density drop becomes extremely steep and the liquid and vapor phases converge.
What temperature range is valid for this calculator?
The temperature lookup mode is calibrated for the stable liquid range at atmospheric pressure: from the melting point at -169.15 C (104 K) to the normal boiling point at -103.74 C (169.41 K). Outside this window at 1 atm, ethylene is either a solid or a gas. For other pressures you need the full equation of state - this calculator does not model pressure effects.
How accurate is the empirical formula used here?
The linear fit rho = 771.35 - 0.456 x T (T in Celsius) is derived from NIST saturation data and is accurate to within about 1-2 kg/m3 (0.2-0.3%) across the full liquid range. For commercial flow metering, pipeline custody transfer or research purposes where tighter accuracy is needed, use NIST REFPROP, which implements the full reference equation of state by Jahangiri et al. (1986) valid to 0.1% or better.
How is this different from ethane or ethanol density?
Ethylene (C2H4), ethane (C2H6) and ethanol (C2H5OH) are three different compounds with very different densities in their liquid states. Liquid ethane at its boiling point (-89 C) has a density of about 544 kg/m3. Liquid ethanol at room temperature is about 789 kg/m3. Ethylene is lighter than both ethanol at ambient conditions and slightly denser than ethane at comparable cryogenic temperatures.
Can I use this for liquefied ethylene gas (LEG) cargo calculations?
Yes, for first-approximation cargo calculations at atmospheric storage conditions. For final bill-of-lading calculations on LEG tankers, the density should be measured directly on board (typically by load cell or pressure gauges on calibrated tanks) and cross-checked with ASTM or ISO standard tables. The temperature lookup in this calculator gives the right order of magnitude and is a useful sanity check against onboard instrumentation.
What units does this calculator support?
Temperature inputs: Celsius, Kelvin or Fahrenheit. Mass inputs: kilograms, grams, pounds or metric tonnes. Volume inputs: litres, millilitres, cubic metres, cubic feet or US gallons. Density outputs: kg/m3, g/cm3, lb/ft3 and lb/gal (all four are shown simultaneously).