Rating system of the Royal Navy

The earliest categorisation of Royal Navy ships dates to the reign of King Henry VIII. Henry's Navy consisted of 58 ships, and in 1546 the Anthony Roll divided them into four groups: 'ships, galliasses,[Note 1] pinnaces, and row barges.' "[2]^: 128[q 1]

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"[Note 2] 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:

• Royal Ships (the largest ships in the previous "great ships" grouping) mounting 42–55 guns and carrying at least 400 men;[3]
• Great Ships (the rest of the ships in the previous "great ships" grouping) mounting 38–40 guns;
• Middling ships mounting 30–32 guns; and
• Small ships mounting fewer than 30 guns

A 1612 list referred to four groups: royal, middling, small and pinnaces; but defined them by tonnage instead of by guns, starting from 800 to 1200 tons for the ships royal, down to below 250 tons for the pinnaces.[2]^: 128[q 2]

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.[1]

The earliest rating was based not on the number of guns, but on the established complement (number of men). In 1626, a table drawn up by Charles I used the term rates for the first time in a classification scheme connected with the Navy. The table specified the amount of monthly wages a seaman or officer would earn, in an ordered scheme of six rates, from "first-rate" to "sixth-rate", with each rate divided into two classes, with differing numbers of men assigned to each class. No specific connection with the size of the ship or number of armaments aboard was given in this 1626 table, and as far as is known, this was related exclusively to seaman pay grades.[2]^: 128[q 3]

This classification scheme was substantially altered in late 1653 as the complements of individual ships were raised. From about 1660 the classification moved from one based on the number of men to one based on the number of carriage guns a ship carried.[1]

Samuel Pepys, then Secretary to the Admiralty, revised the structure in 1677 and laid it down as a "solemn, universal and unalterable" classification. The rating of a ship was of administrative and military use. The number and weight of guns determined the size of crew needed, and hence the amount of pay and rations needed. It also indicated whether a ship was powerful enough to stand in the line of battle. Pepys's original classification was updated by further definitions in 1714, 1721, 1760, 1782, 1801 and 1817 (the last being the most severe, as it provided for including in the count of guns the carronades that had previously been excluded). On the whole the trend was for each rate to have a greater number of guns. For instance, Pepys allowed a first rate 90–100 guns, but on the 1801 scheme a first rate had 100–120. A sixth rate's range went from 4–18 to 20–28 (after 1714 any ship with fewer than 20 guns was unrated).[1]

A first-, second- or third-rate ship was regarded as a "ship-of-the-line". The first and second rates were three-deckers; that is, they had three continuous decks of guns (on the lower deck, middle deck and upper deck), usually as well as smaller weapons on the quarterdeck, forecastle and poop.

The largest third rates, those of 80 guns, were likewise three-deckers from the 1690s until the early 1750s, but both before this period and subsequent to it, 80-gun ships were built as two-deckers. All the other third rates, with 74 guns or less, were likewise two-deckers, with just two continuous decks of guns (on the lower deck and upper deck), as well as smaller weapons on the quarterdeck, forecastle and (if they had one) poop. A series of major changes to the rating system took effect from the start of January 1817, when the carronades carried by each ship were included in the count of guns (previously these had usually been omitted); the first rate from that date included all of the three-deckers (the adding in of their carronades had meant that all three-deckers now had over 100 guns), the new second rate included all two-deckers of 80 guns or more, with the third rate reduced to two-deckers of fewer than 80 guns.[4]

The smaller fourth rates, of about 50 or 60 guns on two decks, were ships-of-the-line until 1756, when it was felt that such 50-gun ships were now too small for pitched battles. The larger fourth rates of 60 guns continued to be counted as ships-of-the-line, but few new ships of this rate were added, the 60-gun fourth rate being superseded over the next few decades by the 64-gun third rate. The Navy did retain some fourth rates for convoy escort, or as flagships on far-flung stations; it also converted some East Indiamen to that role.[4]

The smaller two deckers originally blurred the distinction between a fourth rate and a fifth rate. At the low end of the fourth rate one might find the two-decker 50-gun ships from about 1756. The high end of the fifth rate would include two-deckers of 40- or 44-guns (from 1690) or even the demi-batterie 32-gun and 36-gun ships of the 1690–1730 period. The fifth rates at the start of the 18th century were generally "demi-batterie" ships, carrying a few heavy guns on their lower deck (which often used the rest of the lower deck for row ports) and a full battery of lesser guns on the upper deck. However, these were gradually phased out, as the low freeboard (i.e., the height of the lower deck gunport sills above the waterline) meant that in rough weather it was often impossible to open the lower deck gunports.[4]

Fifth and sixth rates were never included among ships-of-the-line. The middle of the 18th century saw the introduction of a new fifth-rate type—the classic frigate, with no ports on the lower deck, and the main battery disposed solely on the upper deck, where it could be fought in all weathers.

Sixth-rate ships were generally useful as convoy escorts, for blockade duties and the carrying of dispatches; their small size made them less suited for the general cruising tasks the fifth-rate frigates did so well. Essentially there were two groups of sixth rates. The larger category comprised the sixth-rate frigates of 28 guns, carrying a main battery of twenty-four 9-pounder guns, as well as four smaller guns on their superstructures. The second comprised the "post ships" of between 20 and 24 guns. These were too small to be formally counted as frigates (although colloquially often grouped with them), but still required a post-captain (i.e. an officer holding the substantive rank of captain) as their commander.[4]

The rating system did not handle vessels smaller than the sixth rate. The remainder were simply "unrated". The larger of the unrated vessels were generally all called sloops, but that nomenclature is quite confusing for unrated vessels, especially when dealing with the finer points of "ship-sloop", "brig-sloop", "sloop-of-war" (which really just meant the same in naval parlance as "sloop") or even "corvette" (the last a French term that the British Navy did not use until the 1840s). Technically the category of "sloop-of-war" included any unrated combatant vessel—in theory, the term even extended to bomb vessels and fire ships. During the Napoleonic Wars, the Royal Navy increased the number of sloops in service by some 400% as it found that it needed vast numbers of these small vessels for escorting convoys (as in any war, the introduction of convoys created a huge need for escort vessels), combating privateers, and themselves taking prizes.[4]

^* The smaller fourth-rates, primarily the 50-gun ships, were, from 1756 on, no longer classified as ships of the line. Since not big enough to stand in the line of battle, were often called frigates, though not classed as frigates by the Royal Navy. They were generally classified, like all smaller warships used primarily in the role of escort and patrol, as "cruisers", a term that covered everything from the smaller two-deckers down to the small gun-brigs and cutters.

^* The larger fifth-rates were generally two-decked ships of 40 or 44 guns, and thus not "frigates", although the 40-gun frigates built during the Napoleonic War also fell into this category.

^* The smaller sixth-rates were often popularly called frigates, though not classed as "frigates" by the Admiralty officially. Only the larger sixth-rates (those mounting 28 carriage guns or more) were technically frigates.

^* The ton in this instance is the burthen tonnage (bm). From c.1650 the burthen of a vessel was calculated using the formula ${\displaystyle {\frac {k\times b\times {\frac {1}{2}}b}{94}}}$, where ${\displaystyle k}$ was the length, in feet, from the stem to the sternpost, and ${\displaystyle b}$ the maximum breadth of the vessel. It was a rough measurement of cargo-carrying capacity by volume, not displacement. Therefore, one should not change a measurement in "tons burthen" into a displacement in "tons" or "tonnes".

As of 1905, ships of the United States Navy were by law divided into classes called rates. Vessels of the first rate had a displacement tonnage in excess of 8000 tons; second rate, from 4000 to 8000 tons; third rate, from 1000 to 4000 tons; and fourth rate, of less than 1000 tons. Converted merchant vessels that were armed and equipped as cruisers were of the second rate if over 6000 tons, and of the third rate if over 1000 and less than 6000 tons. Auxiliary vessels such as colliers, supply vessels, repair ships, etc., if over 4000 tons, were of the third rate. Auxiliary vessels of less than 4000 tons—except tugs, sailing ships, and receiving ships which were not rated—were of the fourth rate. Torpedo-boat destroyers, torpedo boats, and similar vessels were not rated. Captains commanded ships of the first rate; captains or commanders commanded ships of the second rate; commanders or lieutenant-commanders commanded ships of the third rate; lieutenant-commanders or lieutenants commanded ships of the fourth rate. Lieutenant-commanders, lieutenants, ensigns, or warrant officers might command unrated vessels, depending on the size of the vessel.[6]