For measuring geometric and mass properties of a finalized geometry, use the Measure options under Results > Evaluation Group or Results > Derived Values. Note that, for historical reasons, Derived Values are referred to as Numerical in the COMSOL API. The Evaluation Group option is a more recent addition to COMSOL Multiphysics and is the recommended option. The examples below applies to the Thermal Microactuator Simplified model, which you can find in the Application Libraries at COMSOL Multiphysics > Multiphysics.

The two code listings below computes the following quantities, using Evaluation Group and Derived Values, respectively:

The first four quantities use purely geometry measure features: MeasureVolume, MeasureSurface, MeasureLine, MeasureDistance.

The last two use the MassProperties feature, which also recomputes volume, so you see the volume twice (once from MeasureVolume, once from MassProperties).

Note that when using Derived Values, the massResult array comes back transposed compared to the array returned by an Evaluation Group.

Instead of using the ASCII letter u for the micro-prefix, you can embed the Unicode micro sign (\u00b5) in your unit strings. For example:

This forces the output to render µm^3 rather than um^3.

Rather than hard-coding geometric entity numbers (for example 155, 167), define a named Explicit selection and reuse it. For example:

Note: If you use the Record Code or Record Method tools, the generated code will match the default user interface behavior, it writes all evaluated results into Evaluation Group tables or Table objects. It will not include direct assignments into double[][] arrays or double variables as shown above. The 2D array format is needed because each evaluation feature can compute multiple expressions or perform parametric sweeps.

To account for the circumferential contribution in revolved geometries, set the intvolume flag on a surface measure (and similar for other measures):