### Comment:
[This youtube video explains it well.](https://www.youtube.com/watch?v=kUjpqjvBaHs) Also check out [this article.](https://www.investopedia.com/trading/using-bollinger-bands-to-gauge-trends/) 
  
 In general, when a stock crosses below the bottom band, it is very likely to go up. When it crosses above the top band, it is very likely to go down.

### REPLY:
Is there an online calculator or app? Or do I have to do my own math every time?

### END.