Throughout Three Decks all naval vessels are arbitrarily classified using the British rating system in force at the time of their launch or acquisition (or by the 1626 system if prior to this date) which includes 'Unrated' as the smallest classification. Vessels that were not formally a part of a national navy are classified by their normal purpose. These separate classifications are; 'Privateer', 'Hired vessel', 'Merchantman', 'Letter of Marque' and 'Other Vessel'; the later also including some purpose built naval vessels which can not be considered as a warship (Sheer hulks for example)
In addition ships may also be classified according to their own national rating system where these exist or hired vessels according to their nominal rate while in service (although this is yet to be implemented in full).

All searches and other references to a ships rate refer to the arbitrarily assigned British rate.


Great Britain
Category1603 1626 1653 1685 1697 1714 1721 1760 1782 1801 1802 1817/02
First Rate400+  90-10094-100100    100-120100
Second Rate 250-300300-39964-9090-9690  90-98  80-99
Third Rate 160-200200-29956-7064-8070-8070-8064-8064-8064-84 70-79
Fourth Rate 100-120140-19938-6244-6450-6050-6050-6050-6250-60 50-69
Fifth Rate 60-7080-13928-3826-4430-40 30-44   36-49
Sixth Rate 40-5050-794-1810-2410-2010-2420-3020-28  24-35

Note that the English rating systems of 1653 and earlier classify ships by the size of crew and not the nominal number of guns carried


France
Category1669 1689
Premier Rang80-110100-120
Deuxième Rang54-7980-99
Troisième Rang40-5050-70
Quatrième Rang30-4044-50
Cinquième Rang18-28 
Fregate Legeres8-16 

Russia
Category1727 1732 1750
First Rate90-10070-10080-100
Second Rate80-886666
Third Rate665454
Fourth Rate54  

Dutch Republic
CategoryUnknown
First Charter80+
Second Charter70-78
Third Charter60-68
Fourth Charter50-58
Fifth Charter40-48
Sixth Charter32-44
Seventh Charter20-30

United States of America
CategoryUnknown
Ship of the Line100-120
Ship of the Line64-99
Frigate24-60

Venice
CategoryUnknown 1700
Primo Rango66-7468-74
Secondo Rango52-6460-66
Terzo Rango40-50 
Quarto Rango0-38 

Ottoman Empire
Category1700/00
üç ambarlı (three-decker)55+ (90+ guns)
Kebir Kalyon (large galleon)50-55 (74-86 gunports)
Sagir Kalyon (small galleon)40-50 (54-74 gunports)

Turkish classifications are based on the length of keel in Ziras. The keel was understood as the length between the upper tips of the stem and sternposts.