Bollinger Bands get treated like magic lines that prices "bounce off." They're nothing of the sort. Strip away the folklore and they're one of the simplest ideas in technical analysis: a moving average with a volatility envelope drawn around it.
What they actually are
Three lines. The middle is a simple moving average — usually 20 days. The upper and lower bands sit a fixed number of standard deviations away from it, typically two. Standard deviation is just a measure of how spread out recent prices have been, so the bands are literally a picture of volatility: wide when the market is jumpy, narrow when it's calm.
That's the whole construction. Everything people claim about Bollinger Bands has to be read through that lens — they describe volatility around a trend, nothing more.
What "touching the band" does and doesn't mean
Because roughly 95% of recent prices fall within two standard deviations, a touch of the upper band means price is at the top of its recent statistical range. Beginners read that as "overbought — sell." But like RSI's 70 line, that's a description, not a signal.
In a strong trend, price walks the band — riding the upper band higher for weeks. A touch is a sign of strength as often as exhaustion.
The band tells you where price sits relative to its recent volatility. What it means depends entirely on the trend it's happening inside — exactly the same trap as reading RSI thresholds in isolation.
The squeeze
The one genuinely distinctive Bollinger signal is the squeeze: when the bands narrow sharply, volatility has collapsed. Quiet periods tend not to last, so a squeeze often precedes a large move — but crucially, it says nothing about direction. It flags that something may be coming, not which way.
A %B of 0.86 puts price high in its band — near, not beyond, the upper edge — while a narrow 3.9% bandwidth shows volatility is compressed. That combination reads as a calm, steady grind higher rather than a stretched blow-off; a squeeze this tight is worth watching for the next expansion, without assuming its direction.
Educational commentary — not advice%B (where price sits between the bands) and bandwidth (how wide they are) are both computed directly from price; the read just interprets them together. (Example reading — a point-in-time snapshot, not current data.)
Takeaways
- Bollinger Bands are volatility — a 20-day average with bands ±2 standard deviations.
- Touching a band isn't a signal. In a trend, price rides the band; a touch can mean strength.
- %B tells you where price sits in the band; bandwidth tells you how wide (volatile) it is.
- The squeeze hints a big move may come — but never which direction.
See the bands on any ticker
Pull up a stock or ETF for Bollinger Bands, %B and bandwidth alongside the trend — computed exactly, explained in context.
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