How to Check Volume and Mass in FreeCAD

Checking the volume and mass properties of a 3D body in FreeCAD is essential for engineering analysis, weight estimation, and manufacturing preparation. While volume is calculated directly from the geometry of the solid, determining the mass requires assigning a material density to the model. This guide outlines the most direct methods to inspect volume, calculate mass, and locate center of mass coordinates in FreeCAD using the graphical interface and the built-in Python console.

Method 1: Using the Property View (Volume Only)

The fastest way to view the raw geometric volume of a body without activating special tools is through the Property editor:

  1. Select the Body or solid feature in the Tree view.
  2. Look at the Property view in the lower-left panel and select the Data tab.
  3. Expand the Shape property (or scroll down to the geometry definitions).
  4. Locate the Volume field.

FreeCAD displays the volume in cubic millimeters (\(mm^3\)) or your default configured units.

Method 2: Assigning Materials to Determine Mass

Because FreeCAD only calculates geometric boundaries by default, a body has zero mass until you define its material density.

  1. Switch to the Part Design Workbench.
  2. Select your body in the Tree view.
  3. Click the Material tool (represented by an icon showing a cylinder or colored palette, depending on your FreeCAD version).
  4. Choose a predefined material from the standard library (such as Steel, Aluminum, or ABS) or define a custom density value (\(kg/m^3\)).
  5. Click OK to apply the material.
  6. Select the body or the applied material in the Tree view to view the calculated Mass field within the Data tab of the Property view.

Method 3: Using the Shape Properties Inspection Tool

For a complete breakdown of geometric mass properties, including surface area and center of gravity:

  1. Switch to the Part Workbench using the workbench selector.
  2. Select the solid object in the Tree view.
  3. Navigate to the top menu and select Part → Shape properties (or Part → Check geometry).
  4. In the dialog window that appears, navigate to the details tab to view:
    • Total Volume
    • Total Area
    • Center of Mass coordinates (\(X, Y, Z\))

Method 4: Querying Properties via the Python Console

For exact numerical precision or programmatic extraction, you can query properties directly using FreeCAD's built-in Python terminal:

  1. Ensure the Python console is visible by selecting View → Panels → Python console.
  2. Enter the following commands, pressing Enter after each line:
# Get the active body shape
shape = App.ActiveDocument.ActiveObject.Shape

# Print the volume (in mm³)
print("Volume:", shape.Volume)

# Print the Center of Mass coordinates
print("Center of Mass:", shape.CenterOfMass)

# Calculate mass manually (example with aluminum density: 0.0027 g/mm³)
density = 0.0027
mass_grams = shape.Volume * density
print("Mass in grams:", mass_grams)

This console method bypasses interface display rounding and provides exact coordinate data for moments of inertia and centers of gravity.