Mean reversion is one of the most powerful concepts in algorithmic trading: the idea that prices tend to return to their historical average after extreme moves. Bollinger Bands are the perfect tool to identify and trade these extremes.
What Are Bollinger Bands?
Bollinger Bands consist of three lines: a middle band (20-period simple moving average), an upper band (middle + 2 standard deviations), and a lower band (middle - 2 standard deviations). By definition, about 95% of price action falls within the bands.
The Mean Reversion Logic
When price touches or breaks the upper band, it's statistically "overbought" — likely to revert toward the middle. When it touches the lower band, it's "oversold" — likely to bounce back up. This is the core of the Bollinger Bands mean reversion strategy.
Basic Rules
Buy when price touches the lower Bollinger Band. Sell/exit when price returns to the middle band (20 SMA). Short when price touches the upper band. Cover when price returns to the middle band.
Bollinger Band Squeeze: Predicting Breakouts
When the bands narrow significantly (a "squeeze"), it signals low volatility and an impending breakout. The direction of the breakout determines whether to go long or short. This is a different strategy from mean reversion — it's a breakout play.
Avoiding False Signals
The biggest risk with Bollinger Band mean reversion is trading against a strong trend. In a strong uptrend, price can "walk the upper band" — touching it repeatedly without reverting. Filters to add:
- Only take mean reversion signals when ADX is below 25 (ranging market)
- Combine with RSI: only buy at lower band when RSI is below 40
- Use the middle band as your profit target, not the opposite band
- Avoid trading during major news events or earnings releases
Optimizing Bollinger Band Parameters
The default 20-period, 2 standard deviation settings work well for most markets. For more signals, try 20/1.5. For fewer but higher-quality signals, try 20/2.5. Always backtest parameter changes before going live.
Bollinger Bands + RSI: A Powerful Combination
Combining Bollinger Bands with RSI creates a dual-confirmation system. Only buy when price is at the lower band AND RSI is below 35. Only sell when price is at the upper band AND RSI is above 65. This dramatically reduces false signals.
Pro Tip
CAJDA Bot supports multi-indicator strategies out of the box. You can combine Bollinger Bands with RSI, MACD, or any other indicator in the strategy configuration panel.
Build a Bollinger Bands mean reversion strategy in CAJDA Bot and backtest it instantly — free 15-day trial.
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