Density and specific gravity

Density is the ratio of an object's mass to its volume. In most applications, including Dynamics NAV, mass is interchangeable with weight. The unit of measure for density is expressed as a unit of weight per unit of volume (for example, grams per litre.

Specific gravity is the ratio of an object's density to the density of water. Unlike density, specific gravity does not require a unit of measure.

When defining processes, it may be necessary to convert between the weight and volume for items used in formulas. Using the density of the item allows this conversion. If an item has both a unit of weight and a unit of volume assigned to it, its density can be determined.

How density is calculated

To calculate an item's density, enter both a weight and a volume unit of measure as the item's units of measure. Typically, one of these is the item's base unit of measure. Enter the base quantity for the non-base unit of measure in relation to the base unit of measure. For example, with water, the base unit of measure would typically be the unit of volume, such as gallons. As a result, the weight unit of measure) in this case pounds, is entered in relation to the volume unit of measure. There are approximately 8.35 pounds to the gallon, so the base quantity would be 1/8.35, or 0.119760479.

The system calculates item density only if both weight and volume units of measure have been defined for the item. When the appropriate weight unit of measure and volume unit of measure are entered on the Specifications FastTab of the item card, the system uses the entry in the Base Quantity field together with the specific gravity to calculate the item's density.

If you change either of these units of measure, the density is recalculated for the new units. If you change the density or specific gravity, the Base Quantity must be changed to reflect the new value. Because density and specific gravity are calculated from the base quantity for two units of measure, the system adjusts only one of them. If the base unit of measure is a weight, the adjustment is made to the unit of volume. If the base unit of measure is a volume, the adjustment is made to the unit of weight. If the base unit of measure is neither a weight nor a volume, the adjustment is made to the unit of weight.

To learn more about how to enter or change an item density, see How to: Enter Item Density.