Bollinger Bands Explained
Editor's Note: Options are not suitable for all investors. Options involve risks, including substantial risk of loss and the possibility an investor may lose the entire amount invested in a short period of time. Please see the Characteristics and Risks of Standardized Options.
Bollinger Bands are a popular technical analysis tool that helps traders assess price trends and market volatility. By measuring how far a security’s price moves above or below its average, Bollinger Bands provide insights into whether the price is relatively high or low compared to recent trading activity, indicating whether the security is overbought or oversold.
These bands can be applied to various assets, including options and stocks, making them versatile for different trading strategies. Although Bollinger Bands are often used to spot potential opportunities, they often work best when combined with other indicators to confirm trends and reduce the risk of false signals.
Key Points
• Bollinger Bands are technical analysis tools that measure a security’s price relative to its moving average and volatility.
• The bands consist of three lines: a simple moving average and two standard deviation lines.
• Bollinger Bands help identify overbought or oversold conditions and potential price reversals.
• This tool is more effective when used with other indicators like RSI and MACD.
• Bollinger Bands can be useful for day trading but are not predictive on their own.
What Are Bollinger Bands?
Bollinger Bands are a popular tool used in the technical analysis of securities. They are a set of three bands that measure a security’s relative price in comparison to its moving average and recent price volatility.
The center line is typically the 20-day simple moving average (SMA) of a security’s price, plus plotted lines two standard deviations away from the SMA. The bands are plotted positively and negatively from the SMA, which is what measures the volatility of a security, and the trader can adjust them based on their particular use case. These bands expand during periods of volatility and contract during periods of lower volatility, visually demonstrating market conditions.
Bollinger Bands were created to help investors understand whether a security is currently oversold or overbought, which may help determine whether it is likely to increase or decrease in value over time. When the upper band is close to the SMA, traders may see this as an overbought security. When the lower band is close to the SMA, they may consider the security to be oversold.
The bands, and a set of 22 rules about using them for trading, were developed in the 1980s by John Bollinger, a well-known technical trader.
How Do Bollinger Bands Work?
Bollinger Bands are plotted using two parameters: period and standard deviation.
Period is found by calculating the simple moving average of the security a trader is interested in. The calculation generally uses a 20-day SMA, an average of a security’s closing prices over a 20-day period — or roughly a month of trading days.
The first data point on the graph would be the average of the first 20 days being tracked. The second data point would be the next 20 days, and so on.
That line shows the SMA over time, and the Bollinger Bands are then placed above and below it by calculating the standard deviation of the security’s price along each data point. The standard deviation measures how much a security’s price deviates from its average, reflecting price volatility against its SMA, representing price volatility.
The standard deviation is calculated by first finding the square root of the variance, which is the average of the squared differences of the mean. The standard deviation is typically multiplied by two to create the bands, but traders can adjust this multiplier based on their strategy. The resulting value is then added and subtracted from each SMA data point to form the upper and lower Bollinger Bands.
Key Things to Know About Bollinger Bands
Bollinger Bands adjust dynamically to market conditions, expanding and contracting based on volatility. Here are a few things to keep in mind when using them:
• When volatility is low, the bands get closer together. This contraction reflects a lower volatility period, which may precede future price movements.
• When volatility is high, the bands get farther apart. This indicates that an existing price trend could be coming to a close in the future.
• Generally the security’s price movements stay within the two bands. And once they touch one band they start moving towards the other band. But the price can also bounce off the band multiple times or it can cross over the band. If the price touches one band and crosses the SMA, traders may watch to see if it moves toward the opposite band.
When the price crosses to the outside of the bands, this is a strong indicator of a trend in that direction.
Formula for Bollinger Bands
Below is the formula to plot Bollinger Bands:
BOLU=MA(TP,n)+m∗σ[TP,n]
BOLD=MA(TP,n)−m∗σ[TP,n]
where:
BOLU=Upper Bollinger Band
BOLD=Lower Bollinger Band
MA=Moving average
TP (typical price)=(High+Low+Close)÷3
n = Number of days in smoothing period (typically 20)
m = Number of standard deviations (typically 2)
σ[TP,n]=Standard Deviation over last n periods of TP
Recommended: 7 Technical Indicators of Stock Trading
How Do You Read Bollinger Bands?
Bollinger Bands help traders understand whether a security’s price is relatively high or low so that they might make trades based on trends. Bollinger Bands can indicate uptrends and downtrends as well as possible upcoming price reversals.
Trends with Bollinger Bands can vary based on the asset and trading strategy, lasting anywhere from minutes to years. Traders should understand how to set up the bands based on their timeline. Here are some patterns and indicators traders might want to learn.
Uptrends
Traders can use Bollinger Bands to see whether there is a bullish trend in a security’s market price. If the center line hits the upper band multiple times, this may suggest an uptrend. If the price hits the upper band, decreases but stays above the center line, then hits the upper band again, that is a strong indicator of an uptrend. If the price then hits the lower band, it may indicate a reversal or a loss of strength in the uptrend.
Downtrends
The lower band can indicate a downtrend or an upcoming reversal towards an uptrend. If the price hits the lower band continuously and stays below the center line, this indicates a downtrend. Traders typically avoid making trades during downtrends, but if there is an indicator of a reversal, they might choose to buy.
The Squeeze
When the bands are close together, this is known as a squeeze. The squeeze happens when the security has low volatility, but it indicates that the security will probably have increased volatility in the future. Traders look for high volatility periods to find trading opportunities, so the squeeze reflects decreased volatility and often precedes periods of higher volatility, though it does not predict price direction.
Traders typically like to exit trades during periods of lower volatility, so they look for far-apart bands as a clue that volatility may soon decrease. The squeeze is not used as a trading signal, and doesn’t show whether a security will increase or decrease in value. However, it may help traders figure out the potential timing of upcoming trades.
Breakouts
The SMA line doesn’t always stay between the Bollinger Bands — it can also move above or below the bands. Around 90% of price changes do happen between the bands, so if the price has a breakout above or below the bands it’s a significant event. Breakouts can signal significant price movement outside the bands, however, but they are not reliable predictors of future trends on their own.
Bollinger Band Trading Strategies
Financial analyst Arthur Merrill identified a set of 16 trend patterns, including M patterns and W patterns, that traders can use to recognize potential price reversals. Here are two key patterns.
M Top
The M top pattern indicates that the security price may decrease to a new low. It forms an M pattern at the upper band, where the price nearly hits or hits the upper band but doesn’t cross over it, then decreases to below the low in the center of the M pattern.
W Bottoms
W patterns can be used to identify W bottoms, which is when the second low is lower than the first low but neither low goes below the lower band. If the security rises above the high in the center of the W, this is an indicator that the price will likely reach a new high.
Recommended: How to Analyze Stocks: 4 Ways
Combining Bollinger Bands With Other Indicators
John Bollinger recommended that traders use Bollinger Bands in conjunction with other non-correlated indicators, such as the relative strength indicator (RSI) and the Stochastic Oscillator, in order to gain a comprehensive understanding of the security being assessed.
Although Bollinger Bands help traders understand price volatility and can show opportunities for upcoming trades, they aren’t strong indicators of potential upcoming price movements.
Drawbacks of Bollinger Bands
There are a number of caveats to consider with Bollinger Bands. In particular, they are best used with other stock indicators, to form a fuller picture.
• They show old security price data with equal importance to new data, so data that is outdated may be counted with too much importance.
• They are more of a reactive indicator than a predictive indicator, so they show current market conditions and can indicate trends, but are not strong indicators of what will happen to a security’s price in the future.
• The standard settings of 20-day SMA and two standard deviations is an arbitrary measurement that doesn’t convey relevant information for every security and trading situation, so it’s important that traders understand how to adjust the band calculations for their particular situation.
Using Bollinger Bands for Crypto Trading
Bollinger Bands have become a popular tool for crypto traders to track volatility and trends. They can be used for trading crypto in a similar way to stocks, but some traders choose to use a 28 or 30 SMA instead of 20, to better represent a month of trading days, since the crypto markets are open 24/7.
The Takeaway
Bollinger Bands are a useful tool for technical analysis in options trading, which measure the relative high or low of a security’s price in relation to previous trades over typically the past 20 trading days.
While investors are not able to sell options on SoFi’s options trading platform at this time, they can still employ some of these strategies when they buy call and put options on the platform, whether that’s to try to benefit from stock movements or manage risk.
Investors who are ready to try their hand at options trading despite the risks involved, might consider checking out SoFi’s options trading platform offered through SoFi Securities, LLC. The platform’s user-friendly design allows investors to buy put and call options through the mobile app or web platform, and get important metrics like breakeven percentage, maximum profit/loss, and more with the click of a button.
Plus, SoFi offers educational resources — including a step-by-step in-app guide — to help you learn more about options trading. Trading options involves high-risk strategies, and should be undertaken by experienced investors. Currently, investors can not sell options on SoFi Active Invest®.
FAQ
What do Bollinger Bands tell you?
Bollinger Bands show how a security’s price moves over time, and whether it’s relatively high or low compared to its recent average. They also help gauge volatility: when the bands are far apart, the price is more volatile. When they’re close together, it’s less volatile.
Are Bollinger Bands good for day trading?
Yes, Bollinger Bands can be helpful for day trading because they show short-term price trends and volatility, helping traders spot potential opportunities for quick trades.
How reliable are Bollinger Bands?
Bollinger Bands are useful for identifying trends and volatility, but they’re not foolproof. They work best when combined with other indicators to confirm signals and reduce false predictions.
What indicator pairs well with Bollinger Bands?
The Relative Strength Index (RSI) and the Moving Average Convergence Divergence (MACD) pair well with Bollinger Bands to confirm trends and spot potential reversals.
Photo credit: iStock/blackCAT
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