There are two lines in this oscillator. One is Aroon Up and another is Aroon Down. Aroon Up us calculated by the number of periods minus the number of periods since the highest high divided by the number of periods multiplied by 100. Similarly, the Aroon Down is calculated by the number of periods minus the number of periods since the lowest low divided by the number of periods multiplied by 100. Check the formula section above on this page.