Unit conversions are calculations which convert one product quantity value into a second quantity value, where the two quantities involved are identical.

This is a straightforward calculation. The required unit conversion standard that defines the conversion factor between the two units of measure of the two quantity values just needs to be known.

**Example:**

An oil tank is measured via tank dipping to contain 100 000.0 m³ (quantity: gross observed volume (GOV)) of crude oil.

What is the gross observed volume (GOV) in barrels (bbl) of the crude oil in the tank?

The API MPMS Chapter 11.5 conversion factor from Liter (L) (which is equal to 0.001 m³) to barrel (bbl) is defined as 0.006 289 812, thus the gross observed volume (GOV) of the crude oil is 628 981.2 bbl.

The ASTM D1250-1980 Table 1 conversion factor is defined as 0.006 289 81, which leads to a gross observed volume of 628 981.0 bbl.

**Notes:**

*Unit conversion factors are solely for conversion at the same product temperature and pressure.*