Master and Commander compresses several real ship ratings

Does the film Master and Commander accurately match Jack Aubrey's rank to HMS Surprise?

Not neatly. A 28-gun sixth-rate frigate would normally be a post ship commanded by a captain, while a master and commander more naturally commanded a smaller sloop; the film and novels use artistic license.

Sources describe the fictional Surprise as a 28-gun sixth rate, though the listed battery does not fit that number cleanly. A sixth-rate frigate was a post ship and ordinarily belonged under a post captain. The title master and commander fits a smaller unrated or sloop-type command more comfortably. The adaptation combines names, ships, and incidents from different books, so its command structure serves the story more than a precise Royal Navy establishment table.