Are you a "Solo Cruiser" or a "Single Cruiser"?  Single cruisers seem to want to congregate with other singles while Solo cruisers are comfortable with the concept that they will have a good time on their own.  Whether you are a Solo or a Single you can expect to pay between 150 and 200 percent of the published cruise fare to cover the cost of the missing guest.  Norwegian Cruise Line (NCL) and Princess have been known to charge 200% of the entire fare including government taxes, fuel supplements and fuel charges.

Cunard:
The solo traveler will pay double price for their ships.

Holland America:
More than any other big ship cruise line, is renowned for catering to solo guests.  Not only do they offer programs that don't require partners and activities that can be accomplished solo that are a means to meet others but they also have a Single Partners Program that is a roomate matching service.  Yes, you still have to pay 150% to double but  you will be well cared for.

Peter Deilmann Cruises
With 600 guests it is easy to meet fellow passengers and explore similarities.  Three of the eight 5 star vessels offer 125 to 155 percent discounts for singles.

Silversea Cruises
Offers a Solo Traveler Savings Program which is specifically geared to singles who make up about 10 percent of its passengers.  Only 296 passenters on the Selver Cloud and Silver Wind, and 382 on the Silver Shadow and Silver Whisperer, so it is easy for singles to feel at home.  Book early and you can be offered to pay 110 to 125 percent of the regular fares.

Crystal Cruises
Crystal is perhaps the most popular line for solos, who make up to 15% of its passengers on some sailings.  The programs and dining arrangements are quite attractive to the single traveler.  Look to the January sailings for the best single discounts.

Seabourn
Very intimate cruising, more formal than the rest but depending on the sailing or time of the year discounts could mean you pay 100 to 125 percent tarriff on your accommodations.

Costa Cruises
As much fun as you can have on Costa the cost will most definitely be 200%.