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by Matt Bussey, April 23, 2021

How to Specify Quantity in Bill of Materials

Level 1 Part 4
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Here is our final blog in the Autodesk Inventor BOM Level 100 Series. Stay on the lookout for intermediate and advanced blogs related to BOM coming soon.

The Level 100 topics include:

In our previous posts, we talked about what is Inventor Bill of Materials, showed you how to view BOM and what structure types of BOM are.  Today, we will talk about how to quantify in BOM.

Inventor BOM lets you specify a quantity for components that are something other than the discrete number of occurrences (1, 2, 3, etc.) of the part file in an assembly.  You can specify quantity in terms of Length, Volume, or Mass.

There are three basic properties that represent the quantity of a component, the Base Quantity, the Base Unit, and the Unit Quantity.  These are document settings on the Bill of Materials tab in the Document Settings dialog for the part. They can be set using the Assembly Bill of Materials dialog by adding the Base Quantity and Base Unit columns to the grid.


Base Quantity


Base Quantity is the “raw” quantity for a single instance of a part.  By default, this is “Each”, which means that every occurrence of the part in an assembly adds “1” to the total quantity.

To have a base quantity that is either length, volume, or mass, you must set the Base Quantity document setting to be any model parameter, user parameter, or imported parameter.  Only parameters that have a value as units of length, volume, or mass are valid.  The quantity will update with the parameter, and equations can be used in the parameter

If you want the quantity to be the final length plus some amount of waste for a cut (say 1/16 of an inch), you can set up a parameter that is called “PurchasedLength” for your Base Quantity and set PurchasedLength to be equal to Length + 1/16.

Base Unit


You can think of the base unit as the Unit of Measure for the part.

You may have to design something in one valid unit, but you really report it in another.  For example, you may purchase a structural steel beam in inches have to cut it to 55 millimeters.  You want the quantity to be in inches, so you select inches as the Base Unit.

Unit Quantity


Unit Quantity is just the Base Quantity formatted with the Base Unit. For example, if the Base Quantity is 30 inches, and the Base Unit is millimeters, the Unit Quantity will be 762 mm.

Quantity Overrides

You can override quantities of a component in an assembly to be a static value.  Start the assembly Bill of Materials dialog, and simply type the value into the Quantity cell for the component.  To restore the calculated value, right click on the Quantity cell and select Calculate Quantity.


Autodesk Inventor Bill of Materials allows you to set up quantities other than discrete addition, which better reflects the true Bill of Materials.  Use the Base Quantity to get the raw amount needed, and the Base Unit to keep it formatted properly for communicating the quantity to all your drawings and to Data Management systems, such as Vault Professional.  Quantities can even be manually set to a static value in the assembly BOM.

Check out our next set of post on Intermediate Bill of Materials Topics here!


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