# Using SysML parametric diagrams

Parametric diagrams show mathematical relationships, such as performance constraints, among the pieces of the system being designed.

These diagrams are only available if you are using the SysML profile for your project. Parametric diagrams have the following general uses:

- Indicate the relationships for the objective analysis of functions
- Measure effectiveness
- Clarify the relationship between one variable and another

Parametric Diagrams cannot exist in isolation. They are created using model elements called constraint blocks that define generic or basic mathematical formulas.

To illustrate another possible use for a parametric diagram, a set of constraint blocks could define the volume of a tube, a disc, and the formula for an objects mass (Volume*Density). The parametric diagram would show how these constraint blocks combine, in a particular usage as a set of constraint properties, to give the mass of, perhaps, a tin can or a hollow cylindrical container based upon a set of input parameters. Constraint blocks are created within a block definition diagram, as described in Creating block definition diagrams.