Bollinger Bands in Plain English
What the upper, middle, and lower bands actually tell you — and the mistake everyone makes with them.
· 5 min read · indicator, bollinger, volatility
Bollinger Bands wrap a moving average in a volatility envelope — typically 20-SMA ± 2 standard deviations. When volatility rises, the bands widen; when it falls, they squeeze.
Bollinger Bands chart showing a narrow squeeze region where volatility is low, followed by band expansion and price breaking higher.
The mistake
"Price hit the upper band, so sell." Wrong. In trending markets, price walks along the upper band for long stretches. Touching the band is not a signal by itself — it describes volatility, not direction.
What actually works
- Squeeze: narrow bands = low volatility = impending expansion. Trade the breakout direction.
- Walking the band: in strong trends, pullbacks to the 20-SMA (middle) are entries, not exits.
- Mean reversion in ranges: in a clear range, fade touches of the outer bands.
- Width shift: widening bands with a clean trend = conviction; widening bands with overlap = chop.
Real example: BTC squeeze, October 2023
BTC traded in a tight range through most of September 2023 as Bollinger Bands compressed to their narrowest weekly width since early 2023. On October 1 the bands began expanding, and by October 23 BTC broke above $30,000 with bands fully open — a textbook squeeze-into-breakout. Traders who shorted every touch of the upper band between August and September got steamrolled once the squeeze resolved upward.
Common mistakes
- Treating every upper-band touch as a sell signal without checking whether price is trending or ranging.
- Ignoring the bandwidth itself — a squeeze reading below 10% (bands very close together) is far more actionable than ordinary contraction.
- Fading breakouts from a squeeze; the first few candles of a squeeze expansion often accelerate rather than reverse.
The mental model
Think of bands as a speedometer, not a steering wheel. They tell you how fast the market is moving, not where it is going. Combine with structure and a momentum indicator for direction.
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This article was written and reviewed by the founder. AI tools may assist with drafting; every fact, figure, and example is verified by the author before publishing.