Clay Blair's two-volume tome Hitler's U-Boat War has appendices in the back that comprehensively list how many tons each boat sank on each patrol.
The average tonnage sunk by U-boats gets dragged down during the course of the war, because a lot of U-Boats came back empty-handed or never got to make an attack. The earlier in the war you commanded a U-Boat, the better your boat's averages probably were.
During World War II, some 1,171 U-boats were operational. Of these only some 325 actually carried out attacks on enemy shipping, sinking or damaging the enemy. Over 800 U-boats therefore, were used only on training duties, were never used operationally, or were used but failed to find or attack the enemy or were sunk before ever sinking a ship.
Total Allied shipping losses to U-Boats were in the order of 3,000 vessels representing over 14,000,000 tons. Over 4,000,000 tons of that shipping was sunk by the elite top 3% of the U-Boat commanders. Of all Allied shipping lost 70% was lost to U-Boat attacks. The vast majority of these losses, well over 2,600 vessels, were to torpedo attack alone or a torpedo attack followed by gunfire. Around 160 ships were sunk by deck gunfire alone.
|