Bollinger Bands: A Picture of Volatility

Bollinger Bands wrap price in three lines: a moving average in the middle and a band above and below it. Their real job is to show you one thing at a glance — volatility, how much price is currently spreading out.

How the bands are built

• The middle band is usually a 20-period simple moving average.
• The upper and lower bands sit a set number of standard deviations away from it — commonly two.

Standard deviation is just a measure of how spread out recent prices are. When price swings get wider, the bands move apart. When price goes quiet, they pull in close. The band width is the volatility reading.

The squeeze

When the bands narrow into a tight squeeze, it means volatility has dropped — the market is coiling. Quiet periods tend to be followed by active ones, so traders watch a squeeze as a sign that a larger move may be building. Note: a squeeze tells you a move may be coming, not which direction it will take.

Touching a band is not a signal

The most common mistake is reading “price touched the upper band” as “sell” and “price touched the lower band” as “buy.” In a strong trend, price can walk the band — riding the upper band higher for many candles in a row. Touching a band means price is stretched relative to recent range, not that it must reverse.

How traders actually use them

• Context for range — in a sideways market, the bands roughly mark where price has been over-stretched.
• Volatility timing — squeezes flag low-volatility coils; expansions flag active moves.
• Confirmation — band behaviour is read with price structure, never as a lone trigger.

A realistic expectation

Bollinger Bands describe volatility; they do not predict direction. They are most useful as a backdrop for your price reading, not as standalone signals. Nothing here is financial advice.

Practice it

Reading a squeeze and a band-walk takes reps. Try the Bollinger Bands Practice drill and learn to tell “stretched” from “about to reverse.”