A tuxedo is sized the same as your regular suits. Order the same size.
If you plan to rent, you can visit any tux rental in your town and ask them to measure you for size. They will do it as a courtesy.
I'm a tailor by trade (alterations, not sales), and many years ago worked in a tux rental store. Knowing the typical abilities of the average tux rental clerk, I would recommend getting sized at least twice and take the average(!) But rental wear is for kids to wear at proms and weddings.
A well dressed man has a tuxedo in his closet; not only for cruising, but for special occasions that can be made more special with minimal effort on your part. Ask your wife if she approves of you wearing a tux next time you go out for your anniversary. We look forward to dining out every Christmas Eve in full blacktie.
Again, if you rent more than twice, you are wasting money borrowing used clothes. Invest in a tuxedo, and pack it along with your other suits.