A quick search on the HMS Victory leads us to militarynavalhistory.net, where they have this to say concerning the armaments of the Victory:
The armament comprised thirty 32-pound cannons in the lower gun deck,
twenty-eight 24-pound cannons on the middle gun deck, thirty 12-pound
cannons on the upper gun deck, twelve 12-pound cannons on the
quarterdeck and another two shooting forward on the forecastle. A
special addition was the two 68-pound carronades placed on the
forecastle, able to fire such huge projectiles at short range only.
The carronades were mounted on partially rotating carriages which
allowed to aim them either sidewards or frontally. The ship carried 35 tonnes of gunpowder and 120 tonnes of ammunition to serve her large
artillery battery.
A Tonne is about 2,204.6 pounds, so 77,161 pounds of gunpowder on the Victory. (or 35,000 kg)
A similar figure can also be found in the publication:HMS Victory Pocket Manual 1805: Admiral Nelson's Flagship At Trafalgar
By Peter Goodwin
The Victory had three powder magazines: the grand magazine and two ready hanging magazines. The former, approximately 32
square feet in area and 10 feet high, consisted of three main
compartments creating an industrial assembly line. First was the
pallating flat, containing 35 tons of gunpowder in 784 barrels, each
containing 100lb (45kg) of powder. If ignited, this amount of
gunpowder had the explosive equivalent of 47 tons of TNT.
For comparison, another ship of the line, the French ship César (1768), which was a 74-gun ship, (so a little more average then the Victory), had the following armaments:
César carried twenty-eight 36-pounder guns on her lower deck, and
thirty 18-pounder guns on her upper deck. In addition, sixteen
8-pounder guns were distributed on the fore and aftcastle. In total
César's armament weighed around 215 tons. 6,000 cannonballs, weighing
some 67 tons, were carried. There was also around 8 tons of bar, chain
and grape shot. 20 tons of gunpowder was embarked, stored in the form
of cartridges or in bulk in the depths of the ship. On average, each
gun had 50 to 60 cannonballs.