Density · Temp

Density at temperature calculator

Get the density at the loading temperature, not the lab temperature.

Density quoted on the SDS is at 20 degrees Celsius. Cargo loaded at 40 degrees in a Guangdong summer is less dense, so a tank filled by volume to a weight target overshoots or undershoots the booking. The surveyor reweighs at the gantry and the booking unwinds while the numbers get reconciled.

Pick a preset or type the SDS Section 9 density and the thermal expansion coefficient, then the loading temperature.

Last updated 2026-05-09. Math runs in your browser, no data leaves your computer.

For ISO tank fill math, IMDG 4.2.1.9.5 sets the reference temperature at 50 degrees Celsius. For chargeable-weight calculations, use the temperature at the time of loading.

Pick the closest grade to prefill the reference density and alpha, then override either field below if your SDS reads differently.

Take the value from SDS Section 9, measured at 20 deg C. The presets are typical for the grade, but your supplier's exact concentration shifts it.

The expansion coefficient from a detailed SDS or chemistry handbook. Aqueous solutions sit near 0.0004; light alcohols near 0.0012.

The temperature the cargo actually reaches. Use 50 deg C for IMDG 4.2.1.9.5 fill math, or the gantry temperature for a chargeable-weight check.

Optional. Add the tank's rated volume and the tool also returns the cargo mass at the corrected density, so you can check it against the booking weight.

General guidance only. Verify against the cited primary sources before you commit to a shipment, declaration, or contract.

Density correction in chemical-trade context

Most chemical liquid cargo is quoted in tonnes (mass) but loaded in litres (volume). The bridge between the two is density, and density depends on temperature. A 24,000 L ISO tank loaded with caustic soda 50% at 25 degrees Celsius contains roughly 36,400 kg cargo; the same tank loaded at 50 degrees ambient (which the cargo can reach in transit through the Red Sea) contains roughly 36,000 kg, a 400 kg / 1.1% drop, because the liquid expanded.

For ISO tank fill calculations under IMDG 4.2.1.9.5, the reference temperature is 50 degrees Celsius. The tank must not be filled to a level where, at 50 degrees, the contents exceed the maximum fill volume specified for the cargo class. The density at 50 degrees feeds into that calculation; using density at 20 degrees over-estimates the cargo mass and risks violating the fill rule. Sourzi /tools/iso-tank-loading runs the full IMDG fill math for the most-shipped chemicals.

The thermal expansion formula is straightforward. Density at the target temperature equals reference density divided by 1 plus alpha times the temperature delta. Most liquids have alpha in the 0.0002 to 0.0012 per degree Celsius range. Light hydrocarbons (methanol, ethanol, gasoline) sit at the higher end (0.0010 to 0.0014); aqueous solutions (NaOH 50, citric 50) sit at the lower end (0.0004 to 0.0005); water itself is the lowest at 0.00021.

The alpha values used here are reference values for typical concentrations at typical temperatures; for precise work consult the supplier SDS or a chemistry handbook. The corrections are accurate within 1 to 2 percent across normal trade-temperature ranges (5 to 60 degrees Celsius).

A worked example

You size a 36,400 kg parcel of caustic soda 50% into a 24,000 L tank off the SDS density of 1.5253 at 20 deg C. That is 23,864 L, leaving the tank 99.4% full, which looks loadable on paper.

It isn't. Crossing the Red Sea the cargo warms to 50 deg C, and alpha 0.0004 expands that same parcel to 23,864 x (1 + 0.0004 x 30) = 24,150 L, past the tank's 24,000 L brim. IMDG 4.2.1.9.5 caps the fill at the 50 deg reference precisely so the liquid has room to expand, and this load leaves none. The choice is the one it always is: load less, or load a bigger tank.

Size the parcel to 34,300 kg instead. Cold that is 22,490 L; warmed to 50 deg it expands to 22,760 L, comfortably inside the tank with 5% ullage to spare. The load ships.

Want the tool to run the full IMDG fill math, not just the density step? The ISO tank loading calculator takes this corrected density and returns the binding fill limit for the cargo class at /tools/iso-tank-loading.

Working the ullage and outage side of the same problem? The liquid expansion and ullage calculator sizes the vapour space you need at /tools/chemicals/liquid-expansion-ullage-calculator.

Frequently asked

Why does density change with temperature?

Liquids expand when heated. The volume increases while the mass stays constant, so density (mass per volume) decreases. The thermal expansion coefficient alpha per liquid quantifies the slope. For caustic soda 50% solution alpha is around 0.00040 per degree Celsius; for sulphuric acid 0.00056; for methanol 0.00120; for water 0.00020.

When does the temperature correction matter for chemical trade?

When ISO tank loading at high or low ambient (IMDG 4.2.1.9.5 reference temperature is 50 degrees Celsius for fill calculations); when LCL air-freight where the tank is sealed in cargo hold above ambient; when high-density cargo where 1-percent density change is meaningful for chargeable weight billing; for thermal-expansion-prone cargo like methanol or LPG.

What is the formula?

density(T2) = density(T1) / (1 + alpha * (T2 - T1)). T1 is the reference temperature (often 20 degrees C); T2 is the temperature you want the density at; alpha is the thermal expansion coefficient.

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