Investor's wiki

Bollinger Band\u00ae

Bollinger Band®

What Is a Bollinger Band\u00ae?

A Bollinger Band\u00ae is a technical analysis instrument defined by a set of trendlines plotted two standard deviations (decidedly and negatively) away from a simple moving average (SMA) of a security's price, however which can be adjusted to client inclinations.

Bollinger Bands\u00ae were developed and protected by popular technical trader John Bollinger, intended to discover opportunities that provide investors with a higher likelihood of appropriately recognizing when an asset is oversold or overbought.

Step by step instructions to Calculate Bollinger Bands\u00ae

The most vital phase in working out Bollinger Bands\u00ae is to process the simple moving average of the security in question, normally utilizing a 20-day SMA. A 20-day moving average would average out the closing prices for the initial 20 days as the principal data point. The next data point would drop the earliest price, add the price on day 21 and take the average, etc. Next, the standard deviation of the security's price will be gotten. Standard deviation is a mathematical measurement of average variance and elements conspicuously in statistics, economics, accounting, and finance.

For a given data set, the standard deviation measures how spread out numbers are from an average value. Standard deviation can be calculated by taking the square root of the variance, which itself is the average of the squared differences of the mean. Next, duplicate that standard deviation value by two and both add and deduct that amount from each point along the SMA. Those produce the upper and lower bands.

Here is this Bollinger Band\u00ae formula:
BOLU=MA(TP,n)+m∗σ[TP,n]BOLD=MA(TP,n)−m∗σ[TP,n]where:BOLU=Upper Bollinger BandBOLD=Lower Bollinger BandMA=Moving averageTP (typical price)=(High+Low+Close)÷3n=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\begin &\text = \text ( \text , n ) + m * \sigma [ \text , n ] \ &\text = \text ( \text , n ) - m * \sigma [ \text , n ] \ &\textbf \ &\text = \text \ &\text = \text \ &\text = \text \ &\text {TP (typical price)} = ( \text + \text + \text ) \div 3 \ &n = \text {Number of days in smoothing period (typically 20)} \ &m = \text {Number of standard deviations (typically 2)} \ &\sigma [ \text , n ] = \text n \text \ \end

What Do Bollinger Bands\u00ae Tell You?

Bollinger Bands\u00ae are an exceptionally well known method. Numerous traders accept the closer the prices move to the upper band, the more overbought the market, and the closer the prices move to the lower band, the more oversold the market. John Bollinger has a set of 22 rules to follow while involving the bands as a trading system.

In the chart portrayed below, Bollinger Bands\u00ae bracket the 20-day SMA of the stock with an upper and lower band along with the daily movements of the stock's price. Since standard deviation is a measure of volatility, when the markets become more unstable the bands broaden; during less unpredictable periods, the bands contract.

The Squeeze

The squeeze is the central concept of Bollinger Bands\u00ae. At the point when the bands come close together, constricting the moving average, it is called a squeeze. A squeeze signals a period of low volatility and is considered by traders to be an expected indication of future increased volatility and conceivable trading opportunities. Conversely, the more extensive separated the bands move, the more probable the chance of a reduction in volatility and the greater the possibility of leaving a trade. In any case, these conditions are not trading signals. The bands give no indication when the change might occur or in which direction the price could move.


Around 90% of price action happens between the two bands. Any breakout above or below the bands is a major event. The breakout isn't a trading signal. The mix-up a great many people make is accepting that that price hitting or surpassing one of the bands is a signal to buy or sell. Breakouts give no insight concerning the direction and degree of future price movement.

Limitations of Bollinger Bands\u00ae

Bollinger Bands\u00ae are not a standalone trading system. They are just one indicator intended to furnish traders with information in regards to price volatility. John Bollinger recommends utilizing them with a few other non-connected indicators that give more straightforward market signals. He accepts it is significant to utilize indicators in view of various types of data. A portion of his inclined toward technical strategies are moving average uniqueness/convergence (MACD), on-balance volume, and relative strength index (RSI).

Since they are figured from a simple moving average, they weigh more established price data equivalent to the latest, meaning that new information might be diluted by obsolete data. Likewise, the utilization of 20-day SMA and 2 standard deviations is a bit arbitrary and may not work for everyone in each situation. Traders ought to change their SMA and standard deviation assumptions likewise and monitor them.


  • The upper and lower bands are commonly 2 standard deviations +/ - from a 20-day simple moving average, however they can be modified.
  • There are three lines that form Bollinger Bands: A simple moving average (middle band) and an upper and lower band.
  • Bollinger Bands\u00ae are a technical analysis instrument developed by John Bollinger for generating oversold or overbought signals.