Bluebulb Projects' The Measure of Things presents:
13,000 is about 200 times the number of Submarines in the US Navy.
In other words, it's 180 times the count of Submarines in the US Navy, and the count of Submarines in the US Navy is 0.0056 times that amount.
(a.k.a. Subs) (includes all types, all classes) (2015 figures)