BollingerBands

Bollinger Bands are a volatility-based technical indicator developed by John Bollinger in the early 1980s, consisting of a 20-period simple moving average flanked by upper and lower bands placed at ±2 standard deviations. Because ±2 SD statistically encompasses roughly 95.4% of price action under a normal distribution, a close outside the bands is a statistically rare event — not a routine signal to fade. The indicator’s core insight is that volatility is cyclical: compression follows expansion, and expansion follows compression.

Key Takeaways

• The Bollinger Squeeze — bandwidth at a 6-month low — is the highest-probability setup the indicator produces; trade the direction of the breakout candle, not the squeeze itself.
• A price touching the upper band in a trending market is bullish continuation, not a sell signal; use ADX or volume to determine which regime you are in.
• The %B indicator converts visual band position into a precise number, removing guesswork: values above 1.0 mean price has closed above the upper band, values below 0 mean it has closed below the lower band.

How Bollinger Bands Work

The indicator has three components calculated on every bar:

Middle Band  = 20-period SMA
Upper Band   = 20-period SMA + (2 × 20-period standard deviation)
Lower Band   = 20-period SMA − (2 × 20-period standard deviation)
Bandwidth    = (Upper Band − Lower Band) / Middle Band
%B           = (Price − Lower Band) / (Upper Band − Lower Band)

Middle band: Acts as a dynamic support/resistance level and the mean-reversion anchor. Price crossing the middle band often confirms a regime shift.

Upper and lower bands: Expand during volatile periods and contract during quiet ones. A 20-period default maps to approximately one trading month on daily bars — the most common timeframe for swing traders.

Adjusting settings: Scalpers often shorten the period to 10 for faster signals. For highly volatile assets like Bitcoin, traders commonly widen the SD multiplier to 2.5 to reduce false band-pierce signals.

Three trading regimes Bollinger Bands reveal:

1. Squeeze (pre-breakout): Bandwidth at a 6-month low. Volatility is compressed; an explosive move is building. Wait for the breakout candle to define direction before entering.
2. Trend (band-walking): Price repeatedly closes at or beyond the upper (or lower) band while the middle band slopes. This is continuation — not exhaustion.
3. Reversal (W-Bottom / M-Top): Bollinger’s own documented high-probability patterns. A W-Bottom forms when the second low of a double bottom holds above the lower band, confirming a shift in momentum. An M-Top forms when the second high fails to reach the upper band while ADX is declining.

A useful confirmation layer: when Bollinger Bands expand outside the Keltner Channel — which uses ATR-based bands that are smoother and less reactive — a squeeze breakout is considered high-probability. Bollinger Bands are more reactive to sudden volatility spikes; Keltner Channels smooth through them.

Practical Example

SPY consolidates between $510 and $515 for three weeks. On the daily chart, Bollinger Band width drops to 0.8% — its lowest reading in 8 months. A trader watching for a squeeze sets an alert on bandwidth.

On a Tuesday, SPY closes at $516.50 — a clean break above the upper band at $515.80, on 2× average daily volume. The trader enters at $516.50 with a stop below the middle band at $512.50.

• Risk per share: $4.00
• Account size: $50,000, risking 1% ($500)
• Position size: 125 shares
• Target: upper band + full band width ($8.50 projected move) = ~$524

SPY reaches $523 over the next 6 sessions — a 2:1 reward-to-risk outcome triggered by a textbook Bollinger Squeeze breakout.

Bollinger Bands are three lines on a price chart: a 20-period moving average in the middle with an upper and lower band two standard deviations away. When the bands tighten, a large price move is usually coming. When they widen, volatility is expanding.

Common Mistakes

1. Treating every band touch as a trade signal. In a trending market, price walks the upper band without reversing. Always check whether bands are expanding (trend) or contracting (mean-reversion) before deciding which setup applies.
2. Trading the squeeze before the breakout. The squeeze identifies compressed volatility, not direction. Entering before a confirming candle leads to being caught on the wrong side of a false breakout.
3. Using default settings on all instruments. A 2 SD multiplier that works on SPY will produce excessive false signals on ATR-heavy assets like crude oil futures or BTC. Adjust the multiplier to 2.5 for assets with fat-tailed distributions.
4. Ignoring %B. Visual inspection of whether price is “near” a band is imprecise. %B below 0 or above 1.0 gives an exact, quantifiable read that works cleanly in screeners and trade logs.

How JournalPlus Tracks Bollinger Bands

JournalPlus lets traders tag entries with setup type — including squeeze breakouts and band-fade setups — so performance statistics for each Bollinger Band regime appear separately in the analytics dashboard. Over time, traders can see their actual win rate and average R-multiple for squeeze breakouts versus mean-reversion trades, replacing guesswork about which regime works best for their style.