Bollinger Bandwidth: measuring the squeeze as a number

How bandwidth turns band width into a comparable volatility reading, and how to use it to find compression before it releases.

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What it measures

Bandwidth is the distance between the Bollinger bands divided by the basis, expressed as a percentage. It converts the visual width of the bands into a number.

That makes compression detectable programmatically: a bandwidth at its lowest level in six months is a squeeze, and you can screen for it.

It measures volatility relative to price, so it is comparable between instruments in a way raw band width is not.

That comparability is the reason to compute it at all. Two instruments whose bands look equally tight on screen can have very different bandwidths once price level is accounted for, and only one of them is genuinely compressed.

How it is calculated

These are the steps Basis performs, verified against the published definition.

1
Compute the Bollinger bands.
2
Subtract the lower band from the upper.
3
Divide by the basis and multiply by one hundred.

Settings

Setting	Default	Range
Length	20	1 – 500
StdDev	2	0.1 – 10

It inherits the Bollinger settings. Because it is a ratio, changing the multiplier scales every reading by the same factor and leaves the relative picture unchanged — which makes bandwidth unusually safe to compare across charts with different band settings, as long as you compare each against its own history.

How to read it

Low bandwidth means compressed volatility, which historically precedes expansion. It says nothing about direction.
The useful reading is relative: bandwidth at a multi-month low matters, and an absolute number does not.
Bandwidth rising sharply from a low marks the release, and is often a better entry timing tool than the squeeze itself.
A high bandwidth is not a signal to fade. It says the market is moving, which is when trend tools work and mean-reversion tools do not.
The most useful form is a rank rather than a level: bandwidth in the lowest decile of its own last few hundred bars is a squeeze worth watching, and that phrasing survives being applied to any instrument on any timeframe.

Where it misleads

Dividing by the basis means bandwidth is undefined when the basis approaches zero, and unstable on instruments whose price has moved by orders of magnitude across the lookback — a comparison of today’s bandwidth against a period when price was a tenth of current levels is not measuring the same thing. Compare bandwidth against its own recent history, not against a long one.

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Bollinger Bands Bollinger %B Squeeze Momentum

Updated 2026-08-22 · Educational reference, not financial advice.