Viking Ferry Helsinki --> Stockholm

For me, sitting up on deck is no better than trying to sleep on an airplane and not preferable to sleeping in a decent, flat bed. I've slept well on overnight ferries when I had a bed, and not well when I didn't. While I've shared a cabin years ago, Viking's FAQ section (when you find it) makes clear that the whole cabin is reserved just for you at the price displayed: https://www.sales.vikingline.com/aboard/cabins/.

Yes, I've just found that now Viking sells you the entire cabin. I was working off information from Rick's article " Living It Up on the Stockholm–Helsinki Overnight Boat" in which he writes

"in summer, a one-way ticket per person for the cheapest bed that has a private bath (in a tight, windowless, below-cardeck "C"-class stateroom shared with other travelers) costs €35–€80" which I interpreted as sharing with strangers, as on trains. Guess that was wrong.

[edited] While the competing Silja/Tallink line also sells the whole cabin for one price in the most promoted (top of page) booking options, they do have a link to look further for shared cabins, separated by gender, and some special cabin requests. So you wouldn't book a shared cabin without it being clearly described.

Unless it states otherwise, you are booking the whole cabin.

Silja offers shared cabins but this is made clear in the description.

I travel on both Silja and Viking monthly. I live in Turku so I use the Viking Grace and the Baltic Princess ships. They are both evening ships and depart about 830 pm, arriving in Stockholm around 8 am. Turku has also two morning ships every day, 365 a year. I purchase my tickets directly form each ship's internet site and get great prices, often I pay 22 euros for a window cabin as a frequent passenger. Neither ship sells shared cabins. This sharing does not exist on the Turku Stockholm route. The cabin price is the same regardless if one or four people are in it.
As this route is shorter, the ships make the round trip in 23 hours, staying in port only an hour. I always sleep in and never leave the ship, instead I make it a mini cruise. I enjoy the ship's shows and shop. The Viking Grace is the newest and biggest and the cleanest (runs on LNG gas) of all the Baltic ships, with the largest tax free shop afloat in the world. The Baltic Princess is the same size, 2800 passengers, and has equally great shopping and entertainment. January sales are awesome!

The Turku Stockholm route is great as it has only 90 minutes of open sea, a fact to consider if it is stormy (Fall and Winter). First you have the beautiful Turku archipelago, then the Åland Islands, then the 90 minutes of open sea, and the rest is the Stockholm archipelago. Both ships are made in Finland, and one Christmas I took a special cruise to Riga on the Baltic Princess and we came home in 9.4 meter waves, safe and sound.
Both ships have a special Friday night and Saturday night departure policy that they do not sell alcohol on the outbound trip to keep the drunkenness at a minimum. The rest of the week is very peaceful and this rule does not apply.
Many tourists have found this route as it is a very inexpensive and fun way to spend a night and get to Stockholm. Many locals book several cruises back to back when they have some repairs done at home and they need to be absent, it is less expensive than any hotel!
I feel very privileged to live in a historical cultured city that has such fabulous ships leaving from my door step. I just love it!

Hi Question - Marjatta

When you say "Both ships have a special Friday night and Saturday night departure policy that they do not sell alcohol on the outbound trip to keep the drunkenness at a minimum." Are you referring to the Friday evening departure from Turku? We are very worried about the partying and the booze cruise that I have seen it called for the weekend evening ferry.

My wife and I will be in Turku in late June and plan to take the ferry to Stockholm. We could go Friday evening or do a day trip on Saturday. The Saturday trip might give more chances to view the scenery. We are open to either although my wife can get motion sick very easy and so the day cruise might be better for her.

To superboiler: Yes, they have added that no-liquor-sales-policy for Friday and Saturday night departures, only one bottle of champagne or a bottle of wine is allowed to be purchased. This is to curb the partying of young people. The ships tailor the artists and entertainment to the young people on those two departures. As a retiree, I travel on Sunday night to Thursday night departures, and have had no problem with noise or drunken people.
If your wife gets sea sick easily, the Turku departure is ideal. There is only 90 minutes of open ocean, so you can take a nap in that time, or be in bed for the night. Works wonderfully for me!
There are lots of Asian tourists on board, as they have discovered this inexpensive 'hotel' night in expensive Scandinavia. And on the Turku route, you pay for the entire cabin, one price regardless if there is one or four people in it. I am often alone in a cabin for four. The shared cabins are not happening here! Happy travels and enjoy the beautiful scenery!