PSY (Psychological Line): calculation and reading

PSY calculates what share of the days in a recent period closed higher.

Updated：2026-11-08

Calculation

PSY = number of days among the last N days whose close was higher than the previous day’s ÷ N × 100 (%), with a default N = 12.

For example, if 7 of the last 12 days closed higher, PSY is 7 ÷ 12 × 100 ≈ 58.3.

How to read it

• The value falls between 0 and 100: 50 means up days and non-up days are equal in number; the higher the value, the more days have risen recently.
• The chart on this site draws two reference lines at 25 and 75. They are common places to look and are used only to describe which range the value falls in.

Limits

PSY only counts how many days rose and ignores how much they rose, so a gain of NT$0.5 and a gain of NT$10 weigh the same in this indicator; unchanged days do not count as up days. It does not predict the future.

This article only explains the calculation and how to read a chart. It is not investment advice.