Density Calculation versus Temperature and Composition

- Fuel density handling tips -

Density prediction of final product before fuel (or each liquids) blending from different composition may be mission impossible without experience and feeling. Overdose may cause improper fuel quality and moreover – fuel degradation. Whether as mixing is performed in industrial or domestic condition there are some useful tips to keep density in limits.

Density vs Temperature

Density of liquid depends on temperature and composition. If temperature increases, density decreases. If temperature decreases, density increases. It is physical property of liquids. Some of them are more resistant on temperature changing, for example water. Others, lets say hydrocarbons, being more expended or compressed. Fuel density is specified by ISO and national standards (ASTM, GOST, DIN etc.). All these organizations have standardized table ‘density – temperature relation’ for each fuel. Unfortunately, the tables are copyrighted, so I can only publish changes and dependencies based on my personal experience which are quite enough for density calculation of produced blends, thus can’t be used for production material balance. For those purposes please use ASTM 1250.

The calculations and the formulas are in metric units. To convert in imperial or other units, please use density unit converter here

Density range 630-810 kg/m³ (Gasoline, Virgin Naphtha): Every temperature grade changes the density by 0.9kg/m3.
Density range 810-900 kg/m³ (Diesel, Biodiesel): Every temperature grade changes the density by 0.8kg/m³.
Density range 900-1000 kg/m³ (Diesel, Biodiesel): Every temperature grade changes the density by 0.7kg/m³.

Example: Density of diesel fuel is 833.0kg/m³ at 20⁰C. Increasing the temperature at 21C will decrease density to 832.2 kg/m³; decreasing the temperature at 12C will increase the density to 839.4 kg/m3 (833.0 + (20-12)*0.8 = 839.4)

Volume Correction Factor
In production material balancing, the volume is variable due to density dependence on temperature. Therefore, mass can’t be simple calculated by formula: m = ρ*V. There have to be included Volume Correction Factor (VCF): m = VCF*ρ*V; again from ASTM 1250

Density vs Composition

The solution of few components has unique density. It depends of constituent amounts. Density of mixture can be calculated by formula:

ρ = (ρ₁V₁/V_t) + (ρ₂V₂/V_t) + (ρ₃ V₃ /V_t) + (ρ_n) V_n) /V_t)


Example: B20 Biodiesel blend is a mixture of 8 gallons (30.28 liters) diesel and 2 gallons (7.57liters) biodiesel. Diesel density is 835 kg/m3, biodiesel density is 875 kg/m3. Temerature of the mixture is 20C. Total volume will be 30.28+7.57 = 37.85 (10 gal)
Density of B20 Biodiesel Blend will be:

ρ = (835*30.28/37.85) + (875*7.57/37.85) = 668 + 175 = 843 kg/ m³ at 20⁰C

I’ve used metric units, but no limit to use other units. Now, temperature influence: 843 + 0.8(20C – 15C) = 847 kg/m3 at 15⁰C. Pressure has not significant influenced on diesel density.

Related Article: Fuel Density: Diesel, Gasoline, Hydrogen, Crude Oil, LPG, Methane and Biodiesel