There are many different ship sizes. In order to make life a bit easier I have composed a list of vessel size groups.
Handy and Handymax: Traditionally the workhorses of the dry bulk market, the Handy and more recent Handymax types remain popular ships with less than 60,000 dwt. A handymax is typically 150-200 meters (492-656 feet) in length, though certain bulk terminal restrictions such as those in Japan mean that many handymax ships are just under 190 meters in overall length. Modern handymax designs are typically 52,000-58,000 DWT in size, have five cargo holds and four cranes of 30 metric ton lifting capacity.
Handymax 'Maple Creek' - 53,474 DWT © Siba Ships S.p.A.
Aframax: Crude and product tankers between 80,000 and 120,000 dwt. This is the largest size defined by the Average Freight Rrate Assessment (AFRA) tanker rate system.
Panamax: Represents the largest acceptable size to transit the Panama Canal, which can be applied to both freighters and tankers; Size is determined principally by the dimensions of the canal's lock chambers, each of which is 33.53 metres (110 ft) wide by 320.0 metres (1050 ft) long, and 25.9 metres (85 ft) deep. The usable length of each lock chamber is 304.8 metres (1000 ft). The available water depth in the lock chambers varies, but the shallowest depth is at the south sill of the Pedro Miguel Locks, and is 12.55 metres (41.2 ft) at a Miraflores Lake level of 16.61 metres (54 feet 6 in). The height of the Bridge of the Americas at Balboa is the limiting factor on a vessel's overall height.
Panamax 'APL Malaysia - 293.99 x 32.20 x 21.80m
Seawaymax: The term Seawaymax refers to vessels which are the maximum size that can fit through the canal locks of the St Lawrence Seaway. Seawaymax vessels are 740 feet in length, 78 feet wide, (maximum 226 m length, 24 m beam) and have a draft of 26 feet (7.92 m). A number of Lake freighters larger than this size cruise the Great Lakes and cannot pass through to the Atlantic Ocean. The size of the locks limits the size of the ships which can pass and so limits the size of the cargoes they can carry. The record tonnage for one vessel on the Seaway is 28,502 tons of iron ore while the record through the larger locks of the Great Lakes Waterway is 72,351 tons. Most new lake vessels, however, are constructed to the Seawaymax limit to enhance versatility by allowing the possibility of off-Lakes use.
Suezmax: This standard, which represents the limitations of the Suez Canal, has evolved. Before 1967, the Suez Canal could only accommodate tanker ships with a maximum of 80,000 dwt. The canal was closed between 1967 and 1975 because of the Israel - Arab conflict. Prior to 1967, a Suezmax was a maximum of 80,000 dwt. Upon reopening in 1975, after many modifications to the locks and canal itself, the maximum was increased to 200,000 dwt.
Suezmax Tanker 'Cap Guillaume' © Euronav
Capesize: Refers to a rather ill-defined standard which have the common characteristic of being incapable of using the Panama or Suez canals, not necessarily because of their tonnage, but because of their size. These ships serve deepwater terminals handling raw materials, such as iron ore and coal. As a result, "Capesize" vessels transit via Cape Horn (South America) or the Cape of Good Hope (South Africa). Their size ranges between 80,000 and 175,000 dwt. Due to their size there are only a comparatively small number of ports around the world with the infrastructure to accommodate such vessel size.
VLCC: Very Large Crude Carriers, 150,000 to 320,000 dwt in size. They offer a good flexibility for using terminals since many can accommodate their draft. They are used in ports that have depth limitations, mainly around the Mediterranean, West Africa and the North Sea. They can be ballasted through the Suez Canal.
Very Large Crude Carrier 'Irene SL' - 319,247 DWT © Auke Visser
ULCC: Ultra Large Crude Carriers, 320,000 to 550,000 dwt in size. Used for carrying crude oil on long haul routes from the Persian Gulf to Europe, America and East Asia, via the Cape of Good Hope or the Strait of Malacca. The enormous size of these vessels require custom built terminals.
Ultra Large Crude Carrier 'Knock Nevis' - 564,650 DWT © Auke Visser