When you make the arrangements to rent a tuxedo from a cruise line, they will tell you what information they want. You probably an figure it all out at home.
For example, Royal Caribbean asks for the following if you want to rent from them:
* Height
* Weight
* Jacket Size
* Chest Size
* Waist Size
* Pant Rise
* Inseam
* Outseam
* Neck Size
* Sleeve Length
Most rentals have adjustable waist bands, but the inseam length is pretty critical. Do you have appropriate shoes?
Personally, I have always used a dark suit and have felt quite comfortable mingling with those wearing tuxedos. I have better things to do with my money than to spend $89 to $99 to rent a tux.
Royal Caribbean Tuxedo Rentals