Hydrocarbon Density Calculator for Engineering Analysis

Calculator inputs

Choose API gravity or enter a known reference density. The calculator applies simplified temperature and pressure corrections for engineering estimates.

Input mode

API gravity (°API)

Reference density (kg/m³)

Reference temperature

Target temperature

Temperature unit

Reference pressure

Target pressure

Pressure unit

Thermal expansion coefficient α (1/°C)

Compressibility coefficient β (1/MPa)

Density output unit

Sample volume

Volume unit

Formula used

This page uses a practical engineering approach for liquid hydrocarbon density. It estimates density from API gravity or a known reference density, then applies temperature and pressure corrections.

1) Specific gravity from API gravity
SG_ref = 141.5 / (API + 131.5)

2) Reference density from specific gravity
ρ_ref = SG_ref × 999.016

3) Temperature and pressure adjusted density
ρ_target = ρ_ref × (1 + βΔP) / (1 + αΔT)

4) Specific volume and mass
v = 1 / ρ_target
m = ρ_target × V

Where α is the thermal expansion coefficient, β is the compressibility coefficient, ΔT is the temperature difference in °C, and ΔP is the pressure difference in MPa. This is suitable for screening, planning, and process checks. It is not a custody transfer table replacement.

How to use this calculator

Select whether your starting value is API gravity or reference density.
Enter the reference and target temperatures.
Choose the temperature unit used in your data.
Enter reference and target pressures with the correct unit.
Provide thermal expansion and compressibility coefficients.
Set an output density unit.
Enter a sample volume if you also want mass.
Click the calculate button to view the result, graph, and export options.

Example data table

These are sample planning values only. Actual product properties vary with composition, pressure, and laboratory reference conditions.

Hydrocarbon stream	API gravity	Reference temp	α (1/°C)	β (1/MPa)	Approx. density
Light naphtha	60	15 °C	0.00110	0.00100	736 kg/m³
Gasoline blend	50	15 °C	0.00095	0.00105	780 kg/m³
Kerosene	42	15 °C	0.00088	0.00110	815 kg/m³
Diesel	35	15 °C	0.00082	0.00115	849 kg/m³
Heavy gas oil	24	15 °C	0.00075	0.00120	906 kg/m³

Frequently asked questions

1) What does this calculator estimate?

It estimates hydrocarbon liquid density at a target temperature and pressure. It also reports specific gravity, API equivalent, specific volume, and mass for a chosen sample volume.

2) Can I start with API gravity instead of density?

Yes. Choose the API option, enter the value, and the page converts it into a reference density before applying the selected temperature and pressure corrections.

3) Why does density drop as temperature rises?

Most hydrocarbon liquids expand when heated. Expansion increases volume faster than mass changes, so density usually decreases as temperature increases under similar pressure conditions.

4) Why does pressure affect density?

Liquids are slightly compressible. Increasing pressure usually makes the same mass occupy a smaller volume, so the estimated density rises modestly with pressure.

5) Is this suitable for custody transfer calculations?

No. This page is best for engineering estimates, quick checks, and planning work. Formal custody transfer usually requires approved standards, tested properties, and certified correction tables.

6) What values should I use for α and β?

Use laboratory data, supplier documents, or plant standards whenever possible. The default numbers are practical placeholders, not universal values for every hydrocarbon stream.

7) Can I export the results?

Yes. After calculation, use the CSV button for spreadsheet work or the PDF button for sharing, filing, or attaching engineering summaries.

8) What unit system does the calculator support?

It accepts Celsius or Fahrenheit, several pressure units, multiple volume units, and density output in kg/m³, g/cm³, or lb/ft³.