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Volatility
Bollinger Bands
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For educational purposes only. Not financial advice. Higher returns come with higher risk. Never risk more than you can afford to lose.
Trading StatementREF: TS-2026-03
Trading StatementFor educational purposes only. Not financial advice. Higher returns come with higher risk. Never risk more than you can afford to lose.
Bollinger Bands, created by John Bollinger in the 1980s, are one of the most widely used volatility indicators in technical analysis. They consist of three lines: a middle band (typically a 20-period simple moving average) and upper and lower bands placed at a specified number of standard deviations (typically 2) above and below the middle band. This construction creates a dynamic envelope around price that expands during volatile periods and contracts during calm ones, adapting to current market conditions.
The genius of Bollinger Bands lies in their adaptability. Unlike fixed-width channels or static support/resistance levels, Bollinger Bands automatically adjust their width based on market volatility. This means the bands provide relevant context regardless of whether the market is in a low-volatility consolidation or a high-volatility trend. Approximately 95% of price action falls within two standard deviation bands, making excursions beyond the bands statistically significant events worthy of attention.
The middle band is a 20-period SMA of closing prices. The upper band is the middle band plus two times the 20-period standard deviation of closing prices. The lower band is the middle band minus two times the standard deviation. Standard deviation measures how dispersed prices are relative to their average. When prices vary widely (high volatility), standard deviation increases and the bands widen. When prices cluster tightly (low volatility), standard deviation decreases and the bands narrow.
The use of standard deviation makes the bands statistically meaningful. With a normal distribution, approximately 68% of data falls within one standard deviation and 95% within two. While price returns are not perfectly normally distributed (they exhibit fat tails and skewness), the two-standard-deviation bands still capture the vast majority of price action. Touches of the outer bands represent moves that are approximately in the top or bottom 2.5% of recent price behavior.
The bandwidth, measured as the distance between the upper and lower bands divided by the middle band, provides a pure measure of volatility. When bandwidth reaches its narrowest point over a lookback period (typically 6 months), the market is in a volatility squeeze that often precedes a significant directional move. John Bollinger himself emphasized that low volatility is often the precursor to high volatility, making the squeeze one of the most important Bollinger Band concepts.
Band width tells the volatility story. Wide bands indicate high recent volatility, while narrow bands indicate low volatility. The transition between these states is key: bands contracting after a period of expansion suggests the volatile move is ending and consolidation is beginning. Bands expanding after a period of contraction suggests a new volatile move is starting. These transitions mark important regime changes.
Price position within the bands indicates relative strength. Price near the upper band shows buying pressure, while price near the lower band shows selling pressure. Bollinger %B quantifies this: it measures where price sits within the bands on a 0 to 1 scale (0 at the lower band, 1 at the upper band, 0.5 at the middle band). Values above 1 or below 0 indicate price has broken outside the bands.
The middle band serves as a mean-reversion target and dynamic support/resistance. In uptrends, pullbacks to the middle band often find buying support. In downtrends, rallies to the middle band often face selling resistance. The middle band effectively divides the Bollinger Band space into an upper zone (bullish) and a lower zone (bearish), with transitions between zones indicating momentum shifts.
The Bollinger Squeeze is the most powerful signal. When the bands contract to their narrowest width in at least 6 months (often measured by the BandWidth indicator or visually), a significant move is approaching. The direction of the breakout from the squeeze determines the trade: enter in the direction that price breaks from the narrow range. Stops are placed on the opposite side of the squeeze range. The logic is that volatility cycles between expansion and contraction, and extreme contraction must eventually resolve into expansion.
Band walks occur in strong trends. During a powerful uptrend, price repeatedly touches or exceeds the upper band, and pullbacks only reach the middle band before resuming higher. The upper band acts as a guide rail rather than resistance. Similarly, during strong downtrends, price walks along the lower band. Recognizing a band walk prevents the mistake of selling at the upper band in a strong uptrend (a common beginner error). Band walks continue until price fails to touch the outer band on a new swing and pulls back to or beyond the middle band.
The W-bottom and M-top patterns are Bollinger's own pattern recognition techniques. A W-bottom occurs when price touches the lower band, bounces to the middle band, makes a second low that may or may not touch the lower band, and then rallies above the middle band. The second low being less extreme than the first (on a %B basis) confirms the pattern. An M-top is the mirror: a touch of the upper band, pullback, a second high that fails to reach the band as convincingly, then a decline below the middle band.
While Bollinger Bands are not a traditional divergence tool, the concept applies through %B. If price makes a new high but %B is lower than at the previous high, price is not as far above its statistical mean as it was before. This is a form of volatility-adjusted divergence: the new high is less extreme in the context of current volatility. Similarly, if price makes a new low but %B is higher than at the previous low, the decline is less extreme statistically.
Combining this %B divergence with RSI divergence creates a powerful two-factor reversal signal. If both price relative to its Bollinger Band position and momentum (RSI) show weakening at new highs, the case for a reversal is much stronger than either signal alone. This combination is particularly effective at identifying M-tops and W-bottoms that lead to significant trend changes.
Bollinger Bands and Keltner Channels together create the Squeeze indicator, popularized by John Carter. When the Bollinger Bands move inside the Keltner Channels (the Bollinger Band width is less than the Keltner Channel width), volatility has compressed to an extreme level. When the Bollinger Bands expand back outside the Keltner Channels, the squeeze has fired. A momentum oscillator determines the direction: positive momentum means the squeeze resolves upward, negative means downward. This is one of the most popular systematic setups in modern technical analysis.
RSI and Bollinger Bands form a natural pair. An RSI reading below 30 combined with price at or below the lower Bollinger Band creates a double-extreme condition that significantly increases the probability of a bounce. Volume indicators add a third dimension: below-average volume during a decline to the lower band suggests selling is exhausting, while above-average volume suggests active distribution. MACD can confirm whether momentum supports the direction of a Bollinger Band breakout from a squeeze, filtering out false breakouts.
TSLA on the daily chart enters a Bollinger Band squeeze. The 20-day bandwidth contracts to its lowest level in eight months as TSLA consolidates between $240 and $260. The Bollinger Bands are inside the Keltner Channels, confirming the squeeze. Momentum (using a 12-period momentum oscillator) is slightly positive and rising.
TSLA breaks above $260 on above-average volume, and the Bollinger Bands begin expanding. The Bollinger Bands exit the Keltner Channels, firing the squeeze. A trader enters long at $262, sets a stop at $248 (below the squeeze consolidation range), and targets $290 based on the measured move from the squeeze range (a $20 range projected from the $260 breakout point).
Over the next two weeks, TSLA rallies to $295 as the bands expand dramatically. Price walks along the upper Bollinger Band, touching it on seven of ten trading days. The trader trails the stop using the middle band (20 SMA), which rises from $250 to $270. When TSLA finally fails to touch the upper band and closes below the middle band at $278, the trailing stop triggers at $275. The trade captured $13 per share (or more with partial exits along the way) from a $14 risk, with the squeeze providing the setup and the band walk providing the ride.
The most common mistake is automatically selling when price touches the upper band and buying when it touches the lower band. While this works in ranging markets, it is devastating in trending ones. During a band walk, price repeatedly touches the upper band, and each touch that triggers a sell leads to a loss as price continues higher. Always determine the market regime first: in trends, trade with the band walk; in ranges, fade the bands.
Another mistake is using Bollinger Bands with settings that do not match the security's characteristics. Highly volatile securities (biotech, crypto) may need 2.5 or 3 standard deviations to prevent constant band touches that diminish the signals' significance. Stable blue chips may work better with 1.5 standard deviations. If price touches the bands too frequently (more than 10% of the time), the bands are too narrow and should be widened. If price never reaches the bands, they are too wide and should be narrowed.
The standard 20, 2 settings (20-period SMA with 2 standard deviations) are the most widely used and tested. These settings were developed by Bollinger himself after extensive research and represent the best general-purpose configuration. For shorter-term trading on intraday charts, settings of 10, 1.5 or 12, 2 can provide faster signals. For longer-term weekly charts, 20, 2 remains effective, or 30, 2 can be used for smoother bands.
When using Bollinger Bands for squeeze detection, the standard settings should be paired with Keltner Channels using 20-period EMA and 1.5x ATR. This combination is the standard squeeze configuration. Adjusting either the Bollinger or Keltner settings changes the squeeze sensitivity. Wider Keltner Channels mean the Bollinger Bands must contract more to trigger a squeeze, producing fewer but more reliable signals. Experiment with settings in backtesting, but start with the standards as they benefit from widespread adoption.
Bollinger Bands are based on the assumption that price returns are roughly normally distributed, which is not entirely accurate. Financial markets exhibit fat tails (extreme moves occur more frequently than a normal distribution predicts) and skewness (asymmetric distribution). This means that the 95% containment rate is approximate, and prices can extend beyond the bands more often than the statistical model suggests, particularly during crisis events or parabolic moves.
The bands are also purely reactive. They widen after volatility has already increased and narrow after it has already decreased. This lag means the squeeze signal occurs after volatility has already compressed (which is by design) but the expansion phase is only confirmed after the breakout has begun. In fast-moving markets, the bands may take several periods to catch up to the new volatility level, during which time the band-based signals are less reliable. Additionally, the use of a simple moving average for the center line means Bollinger Bands lag in trending markets, and the bands can trail behind price during rapid advances or declines.