Index calculation values are calculated and published daily after the market closes, and in some cases they are calculated in real time. Index performance between any two dates can be calculated by dividing the ending index value by the beginning index value as follows. Using our hypothetical index as an example:

Day 1 index value = 100.0

Day 4 index value = 104.2

((104.2 / 100) -1) x 100 = 4.2%