Bollinger Bands Explained: Squeeze and Breakout
Bollinger Bands plot a moving average with two bands set a number of standard deviations away, so the bands automatically widen and narrow with volatility.
- The bands are built from standard deviation, so they widen automatically when volatility rises and narrow automatically when it falls — no manual adjustment needed.
- A "squeeze," where the bands pinch tightly together, often precedes a sharp move, but it doesn’t tell you which direction that move will go.
- Touching a band is not, by itself, a buy or sell signal — in a strong trend, price can ride along a band for an extended stretch without reversing.
- %B and bandwidth turn the bands into two precise numbers instead of a visual read, useful for screening or comparing setups objectively.
Bollinger Bands answer a question moving averages alone can’t: not just where the trend is, but how stretched price currently is relative to its own recent volatility. That second piece, volatility, is what makes them genuinely different from a simple moving-average overlay.
How Bollinger Bands Are Calculated
Middle band = 20-period simple moving average
Upper band = Middle band + (2 × standard deviation of the last 20 closes)
Lower band = Middle band − (2 × standard deviation of the last 20 closes)
Standard deviation measures how spread out recent closes are from their average. When price has been calm, that spread is small and the bands sit close together. When price has been volatile, the spread is large and the bands stretch further apart, automatically, without anyone adjusting a setting.
The Squeeze
When the bands pinch tightly together, it means volatility has compressed to an unusually low level. Volatility tends to move in cycles between calm and active, so a squeeze is generally read as a signal that a bigger move is coming, not that price will stay quiet forever.
The squeeze says nothing about direction. It can resolve upward or downward with equal likelihood on its own — you need a separate signal (a breakout candle, a trendline break, a volume spike) to guess which way it’s likely to go.
A squeeze followed by a breakout above the upper band
Band Walking
A common beginner mistake is treating the upper and lower bands like fixed overbought/oversold lines, the way RSI’s 70/30 levels are used. In a strong trend, price can "walk" the upper band, closing near or outside it candle after candle, for an extended stretch without ever reversing. Selling the very first touch of the upper band in a strong uptrend is a common way to fight a trend that has real momentum behind it.
%B and Bandwidth
%B tells you exactly where price sits within the bands as a percentage: %B = (Price − Lower Band) ÷ (Upper Band − Lower Band). A %B of 1.0 means price is sitting right on the upper band, 0.0 means right on the lower band, and 0.5 means price is at the middle moving average.
Bandwidth measures how wide the bands currently are relative to the middle band: Bandwidth = (Upper Band − Lower Band) ÷ Middle Band. A falling bandwidth reading is the numeric version of a visual squeeze, useful for screening many charts at once instead of eyeballing each one.
Combining Bollinger Bands With a Momentum Indicator
Bollinger Bands describe volatility and relative price stretch, not direction or momentum, which is exactly why they’re rarely used alone. A common pairing is Bollinger Bands with RSI: a price touch of the lower band alongside an oversold RSI reading is treated as a stronger signal than either one showing up by itself, since the two are confirming different things (stretched price and weak momentum) at the same time.
Key takeaways
- The bands widen and narrow automatically with volatility — they measure how stretched price is, not where it will go next.
- A squeeze flags that a bigger move is likely coming, but says nothing about direction until confirmed by something else.
- Never treat a band touch as an automatic reversal signal on its own — check whether the broader trend is strong enough to "walk" the band first.
- %B and bandwidth turn the visual read into exact numbers, useful for comparing setups or scanning across many charts at once.
Common mistakes
- Selling every touch of the upper band and buying every touch of the lower band regardless of the broader trend.
- Assuming a squeeze predicts an upward breakout by default — it says nothing about direction on its own.
- Using Bollinger Bands in isolation instead of pairing them with a trend or momentum indicator.
Frequently asked questions
What are the best Bollinger Band settings?
20 periods and 2 standard deviations is the original, standard setting and remains the most widely used across both stocks and crypto. Some traders tighten it to 1.5 standard deviations for more frequent signals, or widen it to 2.5 for fewer, higher-conviction ones.
What exactly is a Bollinger Band squeeze?
It’s a period where the upper and lower bands pull unusually close together, reflecting a sharp drop in recent volatility. It’s widely watched as an early warning that a larger move is likely coming, though the direction still needs to be confirmed separately.
Do Bollinger Bands work on crypto?
Yes, the calculation is identical. Because crypto is naturally more volatile than most stocks, the bands tend to run wider on average, and squeezes can resolve into sharper, faster moves than the same setup on a typical equity chart.
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Disclaimer: this article is educational content, not financial advice. Markets involve risk, and past behavior does not guarantee future results.
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