I need to create standardized sizes of closed ellipses. It’s for bracelet sizing but it’s good to know how to do this either way.

I have standard length sizes I need, and I need to scale the same ellipse up proportionally to different total lengths (circumference). Is there an obvious command I am just not aware of or is this a legit question?

Again, I need to scale closed and/or open curves to a specific length/circumference.

While calculating the circumference of an elllipse is not a simple task, if you scale it maintaining the ratio of the major and minor axes then the circumference scales proportionately to the length.