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.