As of November 2010, there are 11,127 oil tankers in operation hauling anywhere from 500,000 to 4 million barrels of oil each. The most common haulers are divided into classes based on their deadweight tonnage, the total amount of weight that they can carry, including crew, ballast water, cargo, fuel and provisions.
These crude oil tankers weigh up to 70,000 dead weight tons, with a capacity of 500,000 barrels of oil. This is the largest size vessel that can travel through the Panama Canal.
These tankers weigh from 70,000 to 120,000 dead weight tons, with a capacity of 750,000 barrels of oil. These tankers are the largest tankers in the Average Freight Rate Assessment (AFRA) tanker rate system.