Bollinger Bands, developed by John Bollinger in the 1980s, wrap a moving average with two bands that expand and contract with volatility. They help answer two questions every trader faces: Is price stretched? and Is volatility about to expand?
How Bollinger Bands are built
- Middle band: 20-period simple moving average.
- Upper band: middle band + 2 standard deviations.
- Lower band: middle band − 2 standard deviations.
Standard deviation measures how spread out recent prices are. When the market is volatile, the bands widen; when it is quiet, they narrow.
What the bands tell you
- Price near the upper band: price is high relative to its recent average.
- Price near the lower band: price is low relative to its recent average.
- Bands narrowing (the squeeze): volatility is low — often a calm before a big move.
- Bands widening: volatility is expanding — a move is under way.
Touching a band is not a buy or sell signal by itself. In strong trends, price can "walk the band" — hugging the upper band for many candles.
Strategy 1: Mean reversion
In range-bound markets, price tends to return toward the middle band after stretching to an outer band.
- Entry: close back inside the lower band after closing below it.
- Exit: at the middle band (20 SMA).
- Stop-loss: below the recent low or a fixed percentage.
This works best in sideways markets and struggles in strong downtrends — which is why a stop-loss is essential. Run this exact setup in our Bollinger Bands strategy backtest.
Strategy 2: The squeeze breakout
When the bands become unusually narrow, volatility is compressed. A strong close outside the band after a squeeze often starts a trending move.
- Setup: bands at their narrowest in several months.
- Entry: strong close above the upper band (or below the lower band) with rising volume.
- Exit: close back below the middle band, or a trailing stop.
The challenge is false breakouts. Confirm with volume and the higher-timeframe trend. See breakout trading strategy.
Strategy 3: Trend pullbacks to the middle band
In a strong uptrend, price often pulls back to the middle band (20 SMA) and resumes. Combine it with a bullish candle at that level for an entry, with the stop below the pullback low.
Bollinger Bands with other tools
- RSI: a lower-band touch with RSI divergence can strengthen a mean-reversion idea (RSI guide).
- Volume: confirms squeeze breakouts (volume analysis).
- Support and resistance: bands at a key level carry more weight.
Settings
The default 20-period and 2 standard deviations is a sensible balance. Shorter periods (10) make the bands react faster; wider deviations (2.5) reduce the number of touches. Change one thing at a time and test.
Common mistakes
- Selling every upper-band touch in an uptrend.
- Buying every lower-band touch in a downtrend.
- Using the bands without a stop-loss.
- Ignoring whether the market is trending or ranging — the same band behaviour means opposite things in each.
Risk management
Whether you trade reversion or breakouts, define your stop before entry and size accordingly with the position size calculator. Mean-reversion systems often have high win rates but occasional big losses; test how your system behaves through losing streaks with the Monte Carlo simulator.
Key takeaways
- Bollinger Bands = 20 SMA ± 2 standard deviations; they measure relative price and volatility.
- Band touches are not signals by themselves — context (trend vs range) decides.
- Mean reversion works in ranges; squeeze breakouts work at the start of trends.
- Always use stops and test your rules.
Frequently asked questions
Are Bollinger Bands good for beginners?
Yes, they are visual and intuitive. Just remember that touching a band is not an automatic signal.
What does a Bollinger squeeze mean?
It means volatility is unusually low. Big moves often follow, but the squeeze does not tell you the direction.
Which timeframe is best for Bollinger Bands?
They work on all timeframes. Beginners usually find daily and 4-hour charts clearer.
Can I backtest a Bollinger Bands strategy for free?
Yes — open the Bollinger Bands strategy in our free strategy builder and change any rule.
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