Packing light for formal occassion

You can usually rent formalwear on board ship.

Nancy has solved your mans problem completely, and I agree us women can throw in a lightweight dress and dress it up with some bling and get off easy. My husband has size 13 feet. Just packing one extra pair of his shoes would almost take 1/2 a bag,, LOL

Which cruise line are you going on?

Since cruise lines are notorious for trying to find every which way to part you with your hard earned dollars, Nancy had a good idea about possibly renting formalwear on board. I'd only suggest you contact the cruise line ahead of time and ask if formal attire is available for rent--including shoes--on your particular ship. It may not be cheap, but better than lugging a tux and shoes everywhere.

The other alternative is to bring it with you and then ship it home.

It also seems, nowadays, that a dark suit can pass for formal.

As for what you can wear, well, I'll leave that one to the women on the board.

Thanks everyone to take time to help answer my question! Can't wait for our trip, but much to do before we go.

Here's our carry-on formal nights attire.

For men:

I carry two pairs of pants, one warm-up bottoms (for excercise and pjs), one pair of swim/walking shorts, five shirts (a combination of button up, polo and t-shirts), two pairs of shoes, packable rain shell and lightweight sweater or fleece, plus 3 pairs socks and underwear total (including what I wear on the plane and what I pack).

The only things I add for a cruise (while still staying in a carry-on mode) are a microfiber travel blazer, tie, and pocket square (maybe two ties and pocket squares for different looks). I wear the blazer on the plane so it doesn't go in the carry-on.

The blazer is black (with black rather than brass buttons), one of my button ups (for a cruise) is a white no-iron dress shirt, one pair of pants is black (bamboo rayon, bought to match the blazer), one pair of shoes are Ecco plain toe black dress/walking shoes and my socks are always black crew socks. The chic style these days seems to be normal tip collar, no cumberbund and a long (rather than bow) tie in black, deep red or silver.

It's not a tux, but it looks more formal than many who pack an extra suit just for formal night.

For women:

It's actually easier for women. A black polyester cocktail length dress weighs almost nothing. Dress it up with nothing, silk scarf or costume jewelry (can get multiple looks from one dress).

I would add a pair of very lightweight black sandals that can also be worn to the beach/pool. If you can find a very simple design (preferably in black patent), it would be perfect. Here's some I think would go well (from a two-minute internet search):

http://www.shoebuy.com/carlos-by-carlos-santana-boardwalk/351427/746979

Unfortunately, my wife doesn't feel dressed up unless she's wearing heels - which means a non-versatile pair of shoes in her carry-on. Fortunately, she's tiny enough to carry twice as many items as me in the same amount of space/weight.

We always travel with one bag, even on cruises.

On formal night, we are always surprised by the amount of people who are not in formal attire. You could dress nicely, but not formally and dine. Many others will.

Alternatively, my wife and I usually forgo the dining room and eat in our cabin, or at one of the casual alternatives on the ship. If you have a balcony room, your room steward can arrange for dinner on the balcony.

Once, while in Italy on a cruise, we got a nice dinner to go before boarding the ship. Sat out on the deck and watched the coast of Italy sail by while we dined.

One thing is for sure, you'll be on a cruise, so there is no way you'll go hungry!

Of course, none of these may be the answer you are looking for, but they always work for us.

We were just on a cruise (OK, Mexican Riviera, not Europe) but I noticed that formality has gone way down over the past few years,most likely due to the extra cost of checked bags on airlines. My husband was very badly injured just 12 days before our cruise and was in an arm cast and a wheelchair. There was no way he could get a suit jacket over his cast.We were worried (well, actually that was the least of our worries at the time!) that he would appear overly casual in dress pants and a dress shirt and tie. But once the formal nights came, we noticed that about half the men weren't wearing suits or jackets and he fit right in. Only a few, mostly older men, were wearing tuxes. People this dressy looked more like they were going to the prom or were in a wedding and stood out more than the dressy casuals on board. As long as you look nice and are reasonably dressy, you'll be fine. Everyone was wonderful to us, even if weren't dressed to the nines and we had a good time anyway.