Liquid Ethylene Density Calculator
Find liquid ethylene density from mass and volume, or from a pressure and temperature lookup.
Tabulated at 1, 10 and 50 bar absolute, with 11 volume, 5 mass and 8 density units.
Updated October 19, 2026
What this calculator answers
Liquid ethylene is bought, sold and moved by mass, while the instrument in front of you usually measures volume. This page is the bridge between the two: it turns a mass and a volume into a density, or it looks the density up from the pressure and temperature the liquid is sitting at.
The two groups on the page work independently, and that is deliberate. The first is the definition of density, mass divided by volume, and it solves in any direction: fill in any two of its three boxes and the third is worked out. The second is a lookup. Ethylene's liquid density is published over whole degrees Celsius in three pressure columns — 1 bar(a), 10 bar(a) and 50 bar(a) — and a temperature that falls between two rows is interpolated between them.
The lookup is the path to take when the condition is what you know rather than the weight: a storage vessel at its working pressure, a tanker being filled, a dosing step where the meter counts litres but the recipe is written in kilograms. It is also the path that keeps the answer honest. At −104 °C the 1 bar column reads 576.4 kg/m³ while the 50 bar column reads 563.3 kg/m³, and a single "ethylene density" figure copied from a data sheet cannot serve both of those cases.
In practice that means this page is used for converting tank volume into inventory mass, checking a weighbridge or a flow meter against a known volume, sizing a vessel from a target payload, or quoting a density with the pressure and temperature it belongs to — which is the only form in which the number means anything.
−123 °C to +8 °C
Tabulated liquid range, depending on the pressure column
1 · 10 · 50 bar(a)
Three absolute pressures, one published table each
ρ = m / V
Solved forward, and back to either input
Quick start
Decide which side of the problem you know
If you can weigh the ethylene and measure the volume it fills, use the first group. If what you know is the condition inside the vessel — a pressure and a temperature — use the second. Neither group feeds the other, so working in one of them never disturbs the other.
With a measured mass and volume, enter both
The mass box wants the liquid alone, not the vessel and not a cylinder sitting on a scale, and the volume is the space the liquid actually occupies — for a full vessel, its internal volume. A 100 L dewar holding 57.64 kg of liquid ethylene gives:
The 100 L was converted to 0.1 m³ for the division; enter the volume in whichever unit you measured it in and the same density comes out.
With a pressure and a temperature, look the density up
Choose the absolute pressure that matches the vessel, then enter the liquid temperature. At 1 bar(a) and −104 °C the tabulated row is 576.4 kg/m³, the last row of that column. Pressures are marked (a) because they are absolute pressures, not gauge readings.
A temperature between two rows is interpolated
The tables step in whole degrees Celsius. At 10 bar(a), −103.5 °C sits halfway between the −104 °C row (565.5 kg/m³) and the −103 °C row (563.9 kg/m³), so the mean of the two is returned:
Read the result as a mass per unit volume at that condition
A density on its own is half of a conversion: multiply it by a volume to get a mass, or divide a mass by it to get a volume. The first group does that for you — 528.1 kg/m³ into 30 m³ returns 15,843 kg. Quote the number together with the pressure and the temperature it came from, because the columns disagree by a little over 2% at the same temperature and the reader cannot tell which one you used.
Where the numbers come from
One equation and one set of published tables. The equation is used in the first group, the tables in the second, and both are visible in the formula area under the fields.
The measured group is the definition of density
Mass divided by volume. Rearranged it is a single product, m = ρV, which is why all three boxes are interchangeable: any two of them determine the third. Units are normalised before the division, so a mass in pounds and a volume in US gallons give the same density as kilograms and litres. The value is only meaningful if the whole volume holds liquid: a partly filled vessel, or one holding vapour above the liquid line, is a different problem.
The lookup group interpolates between published rows
Each pressure column lists the liquid density at every whole degree Celsius across the span the data was published for. Between two rows the page draws a straight line:
Over most of each column the neighbouring rows differ by one to three kilograms per cubic metre, and by more near the top of the 50 bar column, where the liquid approaches its critical condition. A straight line across a one-degree step is therefore a very close approximation: the interpolation adds a small fraction of the change between rows, never a new source of error on the scale of the table itself.
What each column covers, and why it stops there
| Pressure column | Last tabulated temperature | Density at −104 °C (kg/m³) |
|---|---|---|
| 1 bar(a) | −104 °C | 576.4 |
| 10 bar(a) | −51 °C | 565.5 |
| 50 bar(a) | 8 °C | 563.3 |
Every column starts at −123 °C. The top of each one follows the phase boundary. At 1 bar the last row is −104 °C, within a degree of ethylene's normal boiling point of 169 ± 1 K, so the top of that column is the warm end of the liquid state. At 50 bar the column ends at 8 °C, just below the critical temperature of 282.5 ± 0.5 K (about 9.4 °C) at a critical pressure of 50.6 bar, above which no amount of pressure produces a liquid at all. Those phase values come from NIST's phase-change data for ethylene.
The bottom of the range is a different kind of limit. −123 °C is simply the first row of the published set; ethylene is still liquid well below it, since it freezes at 103.7 K (about −169 °C). A colder cargo is therefore outside what these tables can answer rather than outside the liquid state, and the page returns nothing there instead of extending the curve.
Inside a single column, temperature is the first-order variable: the 1 bar column falls from 594.5 kg/m³ at −123 °C to 576.4 kg/m³ at −104 °C, a drop of about 3%. The columns also differ from one another at the same temperature, by a little over 2%, because they are three separate published sets. Read the column that matches your working pressure, and compare values within that column.
Worked examples
A weighed dewar checked against the tables
Situation: A 100 L dewar is weighed at 57.64 kg net, sitting at 1 bar(a) and a liquid temperature of −104 °C. Does the weighed density agree with the published data?
Inputs
Result
The lookup group returns 576.4 kg/m³ for the same condition — the last row of the 1 bar column — so the weighed density and the tabulated density agree to every digit the table publishes.
In practice: Treat the agreement as a check on the volume rather than on the scale: the mass is usually the better measurement of the two, so a gap of more than a few tenths of a per cent normally means the dewar's nominal capacity or the fill level behind it is the weak number.
How much ethylene a 30 m³ vessel holds
Situation: A storage vessel of 30 m³ holds liquid ethylene at 10 bar(a) and −80 °C, and the inventory has to be reported as a mass.
Inputs
Result
That is about 15.8 tonnes. Note that −80 °C is above the last row of the 1 bar column, so the 10 bar column is not a refinement here — it is the only column that covers the condition at all.
In practice: Carry the condition into the inventory note. 528.1 kg/m³ at 10 bar(a) and −80 °C is reproducible and checkable; a rounded “about 530 kg/m³” is not.
Getting a number you can trust
Weigh the liquid, not the container
Net mass means the ethylene alone. A cylinder or a dewar standing on a scale carries its own tare, and the error it introduces is a fixed number of kilograms that matters most exactly where precision matters most — small batches.
The three pressures are absolute
A gauge reads pressure above the atmosphere, so 10 barg is roughly 11 bar(a) at sea level. That is not one of the three columns. If the gap between your real pressure and the nearest column is worth more than the table's own spread, the honest move is a reference equation of state rather than the nearest column treated as exact.
Read the temperature of the liquid
In the cryogenic part of the tables a degree is worth roughly one to three kilograms per cubic metre, and a large tank can be a degree or more colder at the bottom than at the top. For a whole-vessel inventory, use a temperature that represents the bulk and write down which temperature you used.
Keep the liquid single-phase
A liquid density only converts a volume into a mass when the whole volume is liquid. If the vessel pressure is close to the saturation pressure for the liquid temperature, part of the volume is vapour and the calculated mass comes out too high. The vapor pressure calculator returns the saturation pressure from a known boiling point and heat of vaporization — ethylene boils at −104 °C at one atmosphere with a molar heat of vaporization of about 13.5 kJ/mol.
Record the condition with the number
Write the triple down: pressure column, temperature, and where the value came from — a measured mass and volume, or the published table. 576.4 kg/m³ is the density at −104 °C in the 1 bar column and nowhere else; without the condition attached, the figure cannot be checked later, and the gap between columns is wider than most of the other errors in an inventory sum.
Questions
Why do the three pressure columns disagree at the same temperature?
They are three separate published tabulations rather than one equation of state sampled at three pressures. At −104 °C the 1 bar column reads 576.4 kg/m³, the 10 bar column 565.5 and the 50 bar column 563.3 — a little over 2% between the extremes. Choose the column that matches your working pressure and read within it; do not read the gap between columns as the effect of pressure alone, which is a question for a reference equation of state.
Why is −50 °C accepted at 10 bar but refused at 1 bar?
Each column stops at the highest temperature at which ethylene is liquid at that pressure. For the 1 bar column that is the normal boiling point, so its last row is −104 °C and −50 °C is past the end of the data. At 10 bar the column runs to −51 °C, so the same temperature is inside the span and the lookup returns 490.1 kg/m³. The shared lower end behaves the same way: below −123 °C there is no published row, even though the liquid itself survives down to about −169 °C.
Do I enter gauge pressure or absolute pressure?
Absolute. The three options are labelled with an (a) for exactly that reason: 1 bar(a), 10 bar(a) and 50 bar(a). A gauge reading has to have the atmospheric pressure added before it can be compared with them, and a real pressure that falls between two columns is not covered by either one precisely — the tables answer the three conditions they were published for.
Can I get a temperature back from a density?
Not from the lookup, and that is why its result is read-only. A density on its own does not identify a temperature: the same value appears at different temperatures in different columns, so there is no single row to point to. The measured group is fully reversible — a density and a volume give a mass, and a mass with a density gives a volume — because mass, volume and density are one equation rather than a table.
How far to trust it
- Interpolated inside a degree, never extrapolated outside a column. Past the last row of a column, or below −123 °C, the page returns no value at all. Those are the edges of the published data, and extending a straight line beyond them would be invention rather than measurement.
- Published values to four significant figures, in three separate tabulations. The columns are not one equation of state, and at −104 °C they sit about 1 to 2% away from a reference equation: NIST gives 567.98 kg/m³ for the saturated liquid at 169.15 K and 572.84 kg/m³ at 50 bar, where these columns read 576.4 and 563.3. The NIST thermophysical property tables for ethylene are the place to check a value when a per-cent difference changes the decision.
- Single-phase liquid ethylene only. Vapour space, two-phase mixtures near the boiling point, and dissolved methane or ethane all change the density and are not modelled here. The field values are for the liquid, at the pressure and temperature you enter, and nothing else.
- The pressure is one of three. 1, 10 and 50 bar(a) are the only conditions with published columns here. If your vessel works at another pressure, no column matches exactly, and the error introduced by using the nearest one is not quantified on this page.
- Planning and checking, not a metering standard. For custody transfer, safety cases, relief-system sizing or vessel design margins, use a measured density or a reference equation of state and have the number reviewed by a qualified engineer. A density this page returns is a good estimate of a real property, not a substitute for the standard your contract or your regulator names.
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