NO, and you shouldn't need one.
Worse case, on your paper, draw the bit positions (right to left ....1, 2, 4, 8, ... out to 16 bits), then above that, write in the corresponding subnet mask (right to left 255, 254, 252, 248 ...).
The whole thing'll take you a minute, maybe two. It'll save you much more than that during the course of the test. There are / were many questions on "Which network does this host belong in?" and how many subnets of how many hosts, stuff like that.
Other than that, learn to count to 31 (in binary) on one hand (Pinky is 1, Ring finger is 2, both are 3, the middle finger is 4 .....etc).
Better yet, learn it until you have it all down cold. Subnetting is fundamental. It is the foundation of many more critical concepts later on.
FWIW
Scott