C257 – API MPMS/GPA TP-27:2007 Density Referral


This calculates the density from standard density or vice versa. Calculation of Ctl is done according to the GPA TP-27 standard. Calculation of Cpl is done according to the relevant API MPMS standard.


GPA Technical Publication TP-27, API MPMS 11.2.4 – Temperature Correction for the Volume of NGL and LPG Tables 23E, 24E, 53E, 54E 59E and 60E (2007)

API MPMS Chapter 11.2.2M – Compressibility Factors for Hydrocarbons: 350 to 637 Kilograms per Cubic Metre Density (15°C) and -46°C to 60°C Metering Temperature (1986)

Measurement of Petroleum Measurement Standards Chapter 11.2.1M – Compressibility Factors for Hydrocarbons: 638-1074 Kilograms per Cubic Metre Range (First Edition August 1984)

Kelton calculation reference C257

FLOCALC calculation reference F064

KIMS calculation reference K213


Solve For

  • Density
  • Standard Density

This option is used to specify which type of density the user wants to convert to and from.

Standard Temperature

  • 15°C
  • 20°C
  • 60°F

This option is used to specify the standard temperature which the calculation is to be based on.


  • Full Precision
  • Rounding

This option is used to specify whether the intermediate values are to be rounded during the calculation as per the standards used.


Temperature correction factor

The temperature correction factor, Ctl, is calculated using the process described in C254

Pressure correction factor

The pressure correction factor, Cpl, is calculated by:

F = Compressibility
P = Pressure
Pe = Equilibrium Vapour Pressure

The compressibility, F, is calculated as per the procedures in C220, the method used is dependent on the density of the liquid.

Standard Density

The standard density is calculated using an iterative calculation that uses the Ctl and Cpl functions to calculate the standard density.