The Crowd Level is based on a scale from 1 to 10, with 1 being least crowded conditions and 10 being most crowded. The scale measures the peak wait time at the Magic Kingdom's three headliner attractions (Space Mountain, Splash Mountain, and Big Thunder Mountain Railroad). Thus, the Crowd Level is a "worst case" scenario, predicting the longest wait at any of these three attractions on a particular day.
1 = Peak wait times of 14 minutes or less
2 = Peak waits of 15 - 24 minutes
3 = Peak waits of 25 - 34 minutes
4 = Peak waits of 35 - 44 minutes
5 = Peak waits of 45 - 54 minutes
6 = Peak waits of 55 - 64 minutes
7 = Peak waits of 65 - 74 minutes
8 = Peak waits of 75 - 84 minutes
9 = Peak waits of 85 - 94 minutes
10 = Peak waits of 95 minutes or more
Source touring plans dot com