The ultimate dream vacation for many people is the world cruise. They’re an opportunity to see many countries and cultures while still relaxing. There’s no packing and unpacking in hotels, no rushing to make a connecting flight, and you can relax and enjoy the pool or shipboard activities while in transit.

One question that often arises is one of time. How long do these cruises take? That varies with the itinerary, and the route taken. Not all world cruises are a complete circling of the globe – those cruises are called a circumnavigation. In general, a world cruise will last anywhere from 80 to 110 days, or longer.

Some cruises actually begin and end at the same port, but some do not. World cruises leaving from the east coast of the United States sometimes end on the west coast, or a cruise beginning in England may end in New York, forgoing the Atlantic crossing. When determining the length of a world cruise, the number of length of port calls will have as much effect as the actual number of miles traveled.

P&O regularly offers short world cruises, short being a relative term, of course. Just like Phileas Fogg in Jules Verne’s classic book, you can go “Around the World in 80 Days”. Even these short cruises cover a lot of ground. For the 2010 season, for instance, the Oriana will visit 19 countries and 28 ports in just 84 days. Cruise vacations of this length usually are not complete circumnavigations, however. There’s simply not enough time.

A more typical world cruise would range around 100 to 115 days, and may or may not be a true circumnavigation. In 2010, Crystal Cruises will offer a 108-day cruise from Miami to London that will include stops in the Middle East and Mediterranean. The Cunard Line will also offer a 99-day circumnavigation from New York to Southampton, including overnight calls in Sydney, Hong Kong and Dubai.

Probably the most spectacular is a 2010 cruise from Cruise West. As cruise vacations go, this one is a whopper, at 335 days, from March 2010 to February 2011. Called the Voyage of the Explorers, the plan is to re-trace routes followed by such famous explorers as Ferdinand Magellan, Marco Polo, and Christopher Columbus. The spectacular itinerary is also accompanied by a spectacular price tag, though, with prices starting around $230,000 (USD).

If you’re dreaming of these fabulous cruise vacations but can’t afford the time or the price tag, take heart. Most cruise lines don’t require that you take the full cruise, but offer the cruise in segments.  Cruise just from Miami to Rio de Janeiro, or Sydney to Singapore, whatever fits your budget and your schedule. A world cruise can be within reach.