I have seen the size restrictions for carryons and am wondering how to interpret them.  it says 16h*30l*24w.  SO  what do those numbers mean?  Is h the length from the top of the bag (i.e handle) to the bottom (i.e. wheels)? Or is that what l means?  Im probably way over thinking this as I tend to do, but any information would be greatly appreciated.

I hope you are talking about carry-ons for the cruise and not a plane, anyway, the dimensions are pretty loose when you are actually in the terminal for embarkation. The measurements do not include the wheels unless they put your bag on their little measuring stand, it is like a stand at the fair or carnival where they measure little kids. It has a big line and they out your bag up against it, if your bag is higher than the line they won't let it through. Keep that in mind. I ususally just use my ll bean backpack for my carry-on that way I don't have to worry.

Yes, Im talking about on the cruise.  i guess the thing is that I want to be able to carryon everything we have.  The suitcase im concerned about is 16*8*25.

Well, if you carry on everything you have you might be lugging it around with you for a while if you have to wait on your room to be ready which I have had to do for the last 3 cruises. but 16x8x25 will probably get through, although there are no guarantees because it is a little too wide.

For Carnival's carry-on purposes, The 16x8 measurement is the critical one, and will fit the entry to the x-ray machine. The 25" measurement could be 40", doesn't matter. ken

Most US airlines (and TSA) have the same requirements for carryon and checked baggage sizes, so let me ask this. Are the requirements for the cruise lines (Carnival in this instance) the same sizes as the airlines?

If my luggage is the proper size to fly, will it be the proper size to cruise?

Are the x-ray machines for the cruise lines the same size and type as the airlines? 

I also have another, somewhat related, question. I will have 1-2 checked bags, a carry on and my laptop case (wheeled). Will I have any issues with the wheeled case and my carry on (both will go through TSA).

I keep seeing people bringing on snacks, beverages, and a number of other things and am wondering if there is a limit to what you bring through security.

Thanks

You can carry on as much stuff as you want as long as it isn't over the size limit. But like another poster said, remember you may have to lug that stuff around the ship for several hours before you can take it to your cabin. Check as much stuff as you can or you'll be sorry, believe me.  Have a great cruise!   Jill