Best way to move elements around screen [uGUI]

I currently want to make some toggle buttons to slide in/out menus when a button is pressed / triggered. My build will be for a variable resolution, so I don't know exactly how far to move the elements using the RectTransform values.

I have another singleton object that checks if the resolution changes (using an Update() comparison) and then fires an event. I use this event to know when to recalculate the offset I have to move the UI elements.

My question is, how do I calculate this value (know resolution changes) and is this the best way to do this?