Bollinger Bands Explained: Volatility, Squeezes and the Overbought Trap
Bollinger Bands are a volatility measure drawn around a moving average. They tell you how unusual the current move is compared with the recent past - which is not the same thing as whether it is about to reverse.
Bollinger Bands are a 20-period moving average with bands two standard deviations above and below, so they widen when price moves more than usual and narrow when it is quiet. A squeeze often precedes a larger move but says nothing about direction. Touching the upper band does not mean overbought: in a strong trend price rides it for long stretches.
Open EURUSD on the H1 in our charting desk with Bollinger Bands already on the chart and look for it on real, current price - the same thing this page describes, on a chart that is moving. It is a free preview of the real desk, and a free guest account is required to open it: put in your email, we send a login code, and you are on a live chart in under a minute. The preview runs real market data with one indicator at a time - nothing is saved and no broker is connected. A preview of the product, not advice.
Open EURUSD with Bollinger Bands →How they are built
Three lines: a middle simple moving average (20 periods by default), and an upper and lower band placed a number of standard deviations away (2 by default). Because standard deviation is calculated from recent prices, the bands widen when the market is moving and contract when it is quiet. John Bollinger introduced them in the early 1980s.
Squeeze and expansion
A squeeze is the bands narrowing, meaning recent price movement has been unusually small. Expansion is the opposite. The useful part of the indicator is that it makes the change between the two visible - a long squeeze often precedes a larger move. It does not say which direction.
Volatility is something you feel on a live chart. Chart Bound replays real tape, free, so quiet and violent markets stop looking the same.
Play free, no signup →The classic misread
"Price hit the upper band, so it is overbought" is the single most common error with this tool. By construction, price spends time outside the bands during any strong move - that is what a strong move is. In a trend, repeated closes near the upper band are evidence of strength, not of an imminent reversal.
When they fail
- Fading the bands in a trend. Selling every touch of the upper band in an uptrend is a losing strategy with a pleasant-sounding rationale.
- The squeeze has no direction. Breakouts from a squeeze fail in both directions; without a level or a structural read you are guessing.
- The 95% figure is a statistical property, not a market law. The "two standard deviations covers about 95%" line assumes a normal distribution, and financial returns have fatter tails, so extreme closes happen far more often than that suggests.
- Settings change the meaning. 20 and 2 are conventions; different values shift how often price touches a band.
- Bands are not support and resistance. They are a calculation from recent prices, not levels anyone is trading against.
Using them sensibly
Use the bands to judge whether the current move is large or small by recent standards, size positions with that in mind (a volatility-based stop does this automatically - see stop loss placement), and take direction from structure and levels rather than from the band itself.
Frequently asked questions
What do Bollinger Bands measure?
Volatility. The bands sit a number of standard deviations from a moving average, so they widen when price moves more than usual and narrow when it is quiet.
Does touching the upper band mean overbought?
No. In a strong trend price rides the upper band for long stretches. Treating a touch as a sell signal is the most common mistake with this indicator.
What is a Bollinger Band squeeze?
A period where the bands narrow because recent movement has been small. It often precedes a larger move, but it does not indicate the direction.
What settings should I use?
20 periods and 2 standard deviations are the defaults. Changing them changes how often price reaches a band, not whether the idea works.
Keep learning
Volatility is something you feel on a live chart. Chart Bound replays real tape, free, so quiet and violent markets stop looking the same.
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