Unrated ship

The rating system of the Royal Navy and its predecessors was used by the British Royal Navy between the beginning of the 17th century and the middle of the 19th century to categorise sailing warships, initially classing them according to their assigned complement of men, and later according to the number of their carriage-mounted guns.

The first movement towards a rating system may be seen in the 15th century and the first half of the 16th century, when the largest carracks in the Navy (such as the Mary Rose, the Peter Pomegranate and the Henri Grâce à Dieu) were denoted "great ships". This was only on the basis of their roughly-estimated size and not on their weight, crew or number of guns. When these carracks were superseded by the new-style galleons later in the 16th century, the term "great ship" was used to formally delineate the Navy's largest ships from all the rest.

The formal system of dividing up the Navy's combatant warships into a number or groups or "rates", however, only originated in the very early part of the Stuart era, with the first lists of such categorisation appearing around 1604. At this time the combatant ships of the "Navy Royal" were divided up according to the number of men required to man them at sea (i.e. the size of the crew) into four groups:

By the early years of King Charles I's reign, these four groups had been renamed to a numerical sequence. The royal ships were now graded as first rank, the great ships as second rank, the middling ships as third rank, and the small ships as fourth rank. Soon afterwards, the structure was again modified, with the term rank now being replaced by rate, and the former small ships now being sub-divided into fourth, fifth and sixth rates.

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