While this is unlikely to be the average, it should provide a relatively accurate impression of the kind of stores carried by and 18th Century ship.
The Victualing Board of the Royal Navy allowed the following provisions for every person serving on one of His Majesty's Ships (per week):
7 Pounds Bisket
7 Gallons of Beer/Measures of Wine
4 Pounds Beef
2 Pounds Pork
2 Pints (Winchester measure) Pease
1.5 Pints (Winchester measure) Oatmeal
6 Ounces Sugar
6 Ounces Butter
12 Ounces Cheese
This was set out as part of Regulations and Instructions - 1808, Relating to His Majesty's service at sea, Section IX, Chapter 1 - Of the Provisions, Article 1.
Article 2 set out suitable substitutions for these measures.
Article XI defines the rules for the provisioning of ships with water:
All His Majesty's, Ships, whether victualled for Channel or Foreign
Service, are to be furnished with as many water casks as their
Captains or Commanders shall demand ; and as the same are to be
supplied of such sizes as the Captains shall apply for, either
leaguers, butts, puncheons, hogsheads, barrels, or half hogsheads, all
Commanders are to have regard thereto, and to apply for such
quantities and species of water cask as they can conveniently stow ;
observing that leagers are to be demanded and supplied for the ground
So, assuming we have a ship with a crew of 150 (Lower estimate of the crew of a Sixth Rate Frigate) - that intends to be at sea for 26 weeks of the year - the following amount of provisions would be required:
27,300 Pounds Bisket
27,300 Gallons Beer
15,600 Pounds Beef
7,800 Pounds Pork
7,800 Pints Pease
5,850 Pints Oatmeal
23,400 Ounces Sugar
23,400 Ounces Butter
46,800 Ounces Cheese
It's worth remembering that it was common for ships of the Royal Navy to carry some livestock for slaughter, milk etc. and the the Captain and Officers of a ship would often buy their own provisions to supplement those supplied by the Victualing Board.