Density & 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 a unit of volume (for example, grams per liter).

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 to be made. 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, both a weight and a volume UOM need to be entered as the item's units of measure. Typically, one of these will be the item's base UOM. The Base Quantity for the non-base UOM is entered as it relates to the base UOM. For example, with water the base UOM would probably be the unit of volume, such as gallons. As a result the weight UOM, in this case pounds, would be entered in relation to the volume UOM. There are approximately 8.35 pounds to the gallon, so the Base Quantity would be 1/8.35, or 0.119760479.

Item density is calculated only if both weight and volume units of measure have been defined for the item. When the appropriate weight UOM and volume UOM are entered on the Specifications FastTab of the item card, the system will use the entry made in the Base Quantity field in conjunction with the specific gravity to calculate the item's density.

If the user changes either of these units of measure, then the density is recalculated for the new units. Also, if the user changes the density or specific gravity, then the Base Quantity needs to be changed to reflect the new value. Since density and specific gravity are calculated from the Base Quantity for two units of measure, the system will adjust only one of them. If the base UOM is a weight then the adjustment will be made to the unit of volume. If the base UOM is a volume then the adjustment will be made to the unit of weight. If the base UOM is neither a weight nor a volume then the adjustment will be made to the unit of weight.

To learn more about how to enter or change an Item density, click here.