Bollinger Bandwidth
Calculate Bollinger Band width and %B indicator
What is this tool?
Bollinger Bandwidth measures the percentage distance between the upper and lower Bollinger Bands relative to the middle band (20-period SMA). It quantifies volatility contraction and expansion cycles. The %B indicator shows where the current price sits relative to the bands (1.0 = upper band, 0.0 = lower band). A narrow bandwidth (squeeze) often precedes significant price movements. Combined with %B, traders identify overbought (>1.0) and oversold (<0.0) conditions.
How to use
- 1
Enter price data
Input a series of closing prices (minimum 20 data points).
- 2
Configure parameters
Set the SMA period (default 20) and standard deviation multiplier (default 2).
- 3
View results
See bandwidth percentage, %B value, band levels, and volatility interpretation.
Frequently Asked Questions
What does Bollinger Bandwidth tell me?
Bollinger Bandwidth measures the relative width of the bands. High bandwidth indicates high volatility; low bandwidth indicates consolidation. The most important signal is the "squeeze" — when bandwidth reaches multi-month lows, it predicts an impending breakout. The direction is typically determined by volume and momentum indicators.
How do I interpret %B?
%B above 1.0 means price is above the upper band (potentially overbought). Below 0.0 means below the lower band (potentially oversold). In trending markets, %B can stay above 1.0 or below 0.0 for extended periods. Use %B with bandwidth — readings are most reliable when bandwidth is expanding from a squeeze.
What is a Bollinger Squeeze?
A Bollinger Squeeze occurs when the bands narrow significantly, indicating low volatility and compressed price action. Low volatility is followed by high volatility — so a squeeze signals an imminent breakout. Traders watch for the squeeze, then enter in the breakout direction when volume confirms. The wider the squeeze, the bigger the subsequent move.
How is Bollinger Bandwidth calculated?
Bandwidth measures how wide the bands are relative to the middle line. It is the difference between the upper and lower band divided by the middle band (the moving average), expressed as a percentage: bandwidth = (upper − lower) / middle × 100. Enter the current price and the three band values; for example an upper band of 110, a middle band of 100 and a lower band of 90 give a bandwidth of 20%. The tool also computes %B, the position of the current price within the bands, (price − lower) / (upper − lower), where values above 1 lie beyond the upper band and values below 0 beyond the lower band.
What are Bollinger Bands?
Bollinger Bands are a volatility indicator made of three lines: a middle 20-period SMA and an upper and a lower band set two standard deviations away from it. In normal market conditions, roughly 95% of price action stays between the bands, so a touch of or break through a band marks an unusually large move.