The Bollinger BandWidth indicator is the numerical difference between the value of the upper Bollinger band and the lower one. As the volatility increases, the Bollinger Bands become wider, and the value of the BandWidth indicator will also increase. As the volatility decreases, the Bollinger Bands become closer, and the value of the BandWIdth indicator will decrease. The BandWidth indicator shows a decrease and an increase in volatility.

It is usually used to find the time of low volatility, when a breakout begins when the price moves to one of the Bollinger bands. If the volatility continues to increase, and the price remains on the same band, this may signal the presence of a trend, as the channel from the Bollinger bands becomes wider.

You can change the input parameters according to the Bollinger Bands indicator included in the standard delivery of MetaTrader. Input parameters:

• BandPeriods: The number of periods for calculating the moving average in the middle of the Bollinger Bands.
• Deviations: The number of standard deviations used to calculate the upper and lower Bollinger bands.