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Indicator Guide > Volatility Indicators > Bollinger Bands
Indicators A ~ Z > Indicators A ~ C > Bollinger Bands
Contents > Indicators A ~ C > Bollinger Bands

Bollinger BandsĀ®

Bollinger Bands were invented by John Bollinger. Used to confirm trading signals, normally from a Momentum Indicator, the bands indicate overbought and oversold levels relative to a moving average.

Bollinger Bands are calculated at a specified number of standard deviations above and below the moving average, causing them to widen when prices are volatile and contract when prices are stable.

Bollinger originally used a 20 day simple moving average and set the bands at 2 standard deviations, suited to intermediate cycles.

Trading Signals

Example 1

Microsoft is charted with Bollinger bands 20 day Bollinger bands at 2 standard deviations.

Microsoft Bollinger Bands

Mouse over chart captions to display trading signals.

Contracting bands warn that the market is about to trend: the bands first converge into a narrow neck, followed by a sharp price movement. The first breakout is often a false move, preceding a strong trend in the opposite direction. A contracting range [C] is evident in June 1998: the bands converge to a width of $2, followed by a breakout in July to a new high.

A move that starts at one band normally carries through to the other, in a ranging market.

A move outside the band indicates that the trend is strong and likely to continue - unless price quickly reverses. Note the quick reversal [QR] in early August.

A trend that hugs one band signals that the trend is strong and likely to continue. Wait for divergence on a Momentum Indicator to signal the end of a trend.

Example 2

Microsoft Corporation: Bollinger Bands 20 day Bollinger bands at 2 standard deviations and Rate of Change 10 day Rate of Change.

Microsoft Bollinger Bands and Rate of Change

Mouse over chart captions to display trading signals.

  1. Go short [S] - bearish divergence on ROC.
  2. Contracting Bollinger Bands [C] warn of increased volatility. This begins with a false rally (note the ROC triple divergence) followed by a sharp fall.
  3. Go long [L] - price hugs the lower band, followed by a bullish divergence on ROC.
  4. Go short [S] - price hugs the upper band, followed by a bearish divergence on ROC.


The default settings for Bollinger bands are 2.0 standard deviations around a 20 day exponential moving average. Edit Indicator Settings to change the standard settings.

See Indicator Panel for directions on how to set up an indicator.

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