← Glossary · Charts and indicators
Bollinger Bands
Two lines around a moving average that show the usual range of swings.
Bollinger Bands place an upper and a lower band around the 20-day average, each two standard deviations away. When prices are calm the bands are close together; when they are volatile, far apart.
A price at or below the lower band is unusually low compared with its recent movement. That can indicate an overshoot to the downside, but in strong downtrends the price can also "ride" the lower band for a long time.