Technical Analysis · Moving Averages and Trend Tools
Bollinger Bands: Measuring Volatility Around a Trend
What You'll Learn
- What the three lines of a Bollinger Band represent
- How the bands widen and narrow, and what that reflects
- What price touching a band is commonly interpreted to mean
The Big Idea
Let me introduce a tool called Bollinger Bands. They take a moving average and wrap it in two additional bands, spaced based on how much price has recently been moving around that average, turning the volatility concept from Reading Markets into something you can actually see directly on the chart.
Let's Break It Down
The middle line of a Bollinger Band is simply a moving average, which you learned about earlier in this module. The upper and lower bands are placed a calculated distance above and below that middle line, based on how much price has recently varied from it — a measurement of recent volatility.
Because the bands are based on recent volatility, they widen and narrow dynamically as market conditions change. During a period of high volatility, from Reading Markets, the bands spread further apart. During a calmer, low-volatility period, they contract closer together.
Price touching or pushing beyond a band is commonly watched as a signal worth paying attention to — though I want you to know it is genuinely interpreted in more than one way. It is sometimes read as price being "stretched" relative to its recent average, and sometimes read as confirming a strong move is underway, depending on the broader context, like the trend and momentum concepts from Reading Markets.
Real Example
Picture a rubber band stretched loosely around a moving object, expanding and contracting based on how erratically that object has recently been moving. During a calm period, the rubber band sits close to the object. During a wild, unpredictable stretch, the band expands significantly to keep up. That is exactly how Bollinger Bands respond to changing volatility.
Why It Matters
Bollinger Bands give volatility, a concept covered more abstractly in Reading Markets, a direct, visual representation right on the chart itself. They are commonly used alongside the trend and momentum tools covered elsewhere in this module, rather than in isolation.
Common Mistake
Please do not assume price touching the upper or lower band always means the same specific thing, like an automatic reversal signal. In practice, it is interpreted differently depending on context, and treating it as one fixed, universal rule oversimplifies what the bands actually reflect.
Quick Check
What do Bollinger Bands widen and narrow in response to?
Key Takeaways
- A Bollinger Band consists of a middle moving average and two outer bands spaced based on recent volatility.
- The bands widen during higher-volatility periods and narrow during calmer ones.
- Price touching a band is commonly watched, but it's interpreted differently depending on broader context, not as one fixed rule.
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