Hey Michael, thanks for pointing that out!
calc() function seems to be a great one.
It occurred too me a little too late that the formula doesn’t have to result in exactly the min/max widths as you pass the breakpoint. It just needs to be less/more than those values, which can be achieved without including the actual width values in the formula, as you’ve demonstrated.
That way, the same formula can be used throughout the email without having to recalculate it for each layout.