Hydrocarbon Mixtures - Molecular Weight vs. Gravity and Average Boiling Point

Calculate average molecular weight of hydrocarbon mixtures based on specific gravity and mean average boiling point using Riazi-Daubert equations (1980 and extended models). Supports both Fahrenheit/Rankine and Celsius/Kelvin temperature scales.

Calculator

Inputs

Temperature Unit

Mean Average Boiling Point (MeABP) (°C / °R / K / °F)

Specific Gravity (S) at 60°F (dimensionless)

Results

MW (Riazi-Daubert 1980)-- kg/kmol

MW (Riazi-Daubert Extended)-- kg/kmol

MW Difference-- %

Temperature Unit	MeABP Value	Specific Gravity	MW (1980)	MW (Extended)	Difference (%)
Celsius	292	0.763	124.6	124.8	0.2
Celsius	298	0.869	217	232	6.5
Rankine	752	0.763	124.6	124.8	0.2
Kelvin	571	0.869	217	232	6.5

Calculation Method

Riazi-Daubert 1980 Model

For Rankine (°R): MW = 4.5673E-05 × TR^2.1962 × S^-1.0164
For Kelvin (K): MW = 1.6607E-04 × TK^2.1962 × S^-1.0164
Valid Range: MeABP 20-400°C, MW 70-300 kg/kmol, API 14-93°

Riazi-Daubert Extended Model

For Rankine (°R): MW = 20.486 × TR^1.26007 × S^4.98308 × e^(1.165E-04×TR - 7.78712×S + 1.1582E-03×TR×S)
For Kelvin (K): MW = 42.965 × TK^1.26007 × S^4.98308 × e^(2.097E-04×TK - 7.78712×S + 2.08476E-03×TK×S)
Valid Range: MeABP 20-560°C, MW 70-700 kg/kmol, API 14-93°
Recommended for: Hydrocarbons > C25, boiling point > 400°C

Where:

TR = Mean Average Boiling Point in °R (Rankine)
TK = Mean Average Boiling Point in K (Kelvin)
S = Specific gravity at 60°F (15.6°C)

Average Error: ~7%

Temperature Conversions:

°F to °R: Add 460
°C to K: Add 273