Very few ships actually have cabins dedicated to solo travelers. These will have sleeping space for one and can be quite small. The studio cabins on select Norwegian ships are the most famous example of this: The 100-square-foot staterooms each contain a full-size bed, nifty lighting effects and a large round window that looks out into the corridor. If you are a solo traveler, you will want to price out the cost of a solo cabin (usually somewhat higher than the double-occupancy rate of a similarly sized stateroom) compared to the cost of paying the single supplement (an extra fee tacked on if there are not two people in a cabin; the price can come out to as much as double the regular rate) for a standard cabin. And book early, as solo cabins sell out quickly.
Cabins are priced based on location on the ship. Typically cabins on lower decks are less expensive. Typically cabins midship (in the middle part of a deck) cost higher. Balcony and Suite cabins on the very aft of the ship can also be more expensive than other cabins.
In order to set the pricing many cruise lines will divide each cabin type into sub categories. For example a balcony cabin may be divided into sub categories such as B1, B2, B3, B4. In most cases the cabin size and features in a sub category is the exactly the same. The only difference is usually the location of the cabin on the ship. Please look for the notes on the category descriptions to determine if there is a difference in size or features between the subcategories.
The "real estate" that your stateroom occupies, no matter the type, can make you seasick or keep you up all night with noise -- or it can lull you like a baby and provide exquisite views of your surroundings. That is why doing your homework is important. Here are some factors to consider when picking your cabins location on the ship.
carnival cruise interior rooms
stateroom on a cruise ship
cruise suites floor plan