Bollinger Bands
Bollinger Bands are a technical analysis indicator composed of three lines plotted on a price chart: a middle band based on a simple moving average, an upper band, and a lower band set at a fixed statistical distance above and below it.[1]
They were developed in the early 1980s by financial analyst and trader John Bollinger, and are used to measure a security's relative high or low price and its volatility, and to identify possible overbought or oversold conditions.[1][2] Because the two outer bands widen and narrow with market volatility, the indicator provides a visual gauge of how prices are dispersed around an average value and where price sits relative to recent trading.[3]
The indicator is applied across asset classes, including stocks, forex, commodities, and cryptocurrencies.[3]
Structure and Calculation
Bollinger Bands consist of three lines. The middle band is the simple moving average (SMA) of a security's price, typically calculated over a 20-day period by averaging the closing prices across those periods.[2] The upper band is set at a level two standard deviations above the middle band, computed by adding two standard deviations to the 20-day SMA, and the lower band sits two standard deviations below it.[2] Under the standard settings, the formulas are middle line = 20-day SMA; upper band = 20-day SMA + (20-day standard deviation × 2); and lower band = 20-day SMA − (20-day standard deviation × 2).[1]
The default configuration most traders use is a 20-period SMA with 2 standard deviations.[3] Positioning the outer bands two standard deviations from the middle line is intended to encompass most price action within the channel. Bybit states this captures approximately 95% of the price action within the upper and lower bands, while Binance Academy presents the figure as at least 85% of price data moving within the two bands; both figures are stated by their respective sources rather than independently verified.[2][1]
Unlike a single moving average, which shows trend direction only and is primarily trend-following, Bollinger Bands measure volatility by adjusting their width based on standard deviation and place current price in a relatively high or low context, allowing them to generate signals for potential overbought or oversold conditions and breakouts.[3] The indicator is described as an oscillator measure that highlights how prices are dispersed around an average value.[1]
Interpretation
The distance between the outer bands reflects market volatility. The bands expand when volatility is high, moving away from the middle line, and contract when volatility is low, moving toward it.[1][2] Over-expanded bands may indicate a trend approaching consolidation or reversal, and when price moves sideways the bands tend to narrow toward the middle SMA.[1]
Price position within the channel offers a read on relative value. When price touches or exceeds the upper band, the market may be overbought; when it touches or falls below the lower band, the market may be oversold.[1][3] The upper band can act as a dynamic resistance level and help traders decide when to enter long positions or exit short positions.[2] A strong price move outside the bands can signal either a potential trend continuation or a potential trend reversal.[3]
The core signal from the indicator is that low volatility and tight deviation levels frequently precede large moves once volatility increases, because volatility tends to revert to its mean.[1][2] Market context matters for interpretation: whether the environment is a bull or bear market and whether the trend is intraday or multi-week can significantly affect how a given band signal should be read.[1]
Trading Strategies
Two named strategies are most commonly associated with the indicator. The Bollinger Bounce trades reversals in a ranging market, entering when price hits an outer band and moves back toward the middle band, based on the idea that price usually returns to the middle band.[2][3] Bybit advises refraining from this strategy during periods of band expansion, when the market is trending rather than ranging.[2]
The Bollinger Squeeze identifies periods of low volatility when the bands contract tightly around the SMA, a condition that often precedes a period of high volatility and an anticipated breakout.[1][2] The squeeze signals a likely large move but is directionally neutral, meaning it does not indicate whether the breakout will be up or down.[1] Confirmation is typically done by observing the Bollinger BandWidth (BBW) reaching a historical low, such as a six-month minimum.[1]
Daily and weekly squeezes tend to carry more weight than intraday ones because they reflect sustained compression over a longer period.[1]
Binance Academy sets out execution guidelines for trading a squeeze. For entry, a trader waits for a confirmed close above the upper band for a long position or below the lower band for a short, ideally accompanied by a volume spike to filter out false breakouts.[1] A stop-loss can be placed below the middle SMA or a recent structural level; one Average True Range (ATR)-based example places the stop at 1.5 times the ATR below the lower band.[1] For taking profit, the guidance is to trail with the SMA until it flattens or price re-enters the bands.[1]
Parameter Settings
Traders can adjust the two settings — the lookback period and the number of standard deviations — to suit different timeframes and trading styles, generating faster or slower signals.[2][3]
Shortening the lookback period and using a smaller standard deviation, such as a 10-day period with 1.5 standard deviations, produces more frequent signals suited to day trading, while a 20-day lookback with 2 standard deviations focuses on longer-term trends and reversals for swing traders.[2]
Binance Academy provides similar horizon-based recommendations: day trading on 1–15 minute charts uses a 10–14 SMA with 1.5–2 standard deviations; swing trading on 1-hour, 4-hour, and daily charts uses the standard 20–21 SMA with 2 standard deviations; and position trading on daily and weekly charts uses a 20–50 SMA with 2–2.5 standard deviations.[1]
For cryptocurrency assets specifically, Binance Academy suggests an 18-period setting for Bitcoin, a 15-period setting for Ethereum, and shorter periods around 9 for smaller altcoins.[1] The standard deviation multiplier can also be adapted to volatility: widening to 2.5 standard deviations suits trend-following breakout strategies on highly volatile assets, while tightening to 1.5 standard deviations suits mean-reversion trades in consolidation zones.[1]
Applications in Crypto Markets
Bollinger Bands are described as particularly suited to short-term trading as a way to analyze volatility and anticipate forthcoming movements.[1]
In equity markets, the indicator has been used to spot extreme short-term price drops and profit from rebounds, and in cryptocurrency markets it is used to gauge volatility and identify potential trends and breakouts.[2]
Limitations
The indicator relies on historical data to determine its standard deviation and band placement, so it may not always predict future price action, and it does not forecast exact prices — it helps assess market conditions and potential setups instead.[2][3]
A key drawback is the risk of false signals, which is most pronounced in choppy or sideways markets.[2] To mitigate this, the guidance is to combine the bands with other indicators, wait for clear signals, and exercise patience and judgment, especially in unstable or ranging conditions.[2]
