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Marks two standard deviations below the moving average, exposing the lower statistical boundary of recent price dispersion.
The lower Bollinger Band sits two standard deviations below the middle band. Prices touching it may indicate the asset is relatively oversold.
The Bollinger Lower Band is the bottom boundary of Bollinger Bands, calculated as the 20-period simple moving average minus two standard deviations of price. This band represents a statistically significant lower boundary that price typically respects. When price touches or breaks below the lower band, it indicates that price is relatively low compared to recent history.
The calculation:
Lower Band = SMA-20 - (2 × Standard Deviation of price over 20 periods)
Example:
SMA-20: $50 Standard Deviation: $2 Lower Band: $50 - ($2 × 2) = $46
Why the lower band matters:
- Oversold indicator: Price at lower band is extended to the downside
- Support zone: Often acts as dynamic support
- Volatility measure: Distance from middle band shows volatility
- Trend weakness: Price consistently at lower band shows strong downtrend
Interpreting price at lower band:
- Touch and bounce: Price may be oversold; watch for reversal
- Walk the band: Strong downtrends see price stay near lower band
- Breakout below: May signal extraordinary weakness or capitulation
- Squeeze breakout: Price breaking lower band after squeeze indicates bearish move
Trading applications:
- Mean reversion: Consider buying when price reaches lower band
- Trend following: In downtrends, sell rallies to middle band
- Breakout trading: Lower band break after squeeze signals bearish move
- Stop placement: Place stops beyond lower band for long positions
Double bottom patterns:
- W-bottom: First low touches lower band, second low inside bands
- Classic Bollinger pattern: Bullish when second low is higher
- Confirmation: Price breaks above reaction high between lows
Common mistakes:
- Automatic buy signal: Price at lower band doesn't always mean buy
- Ignoring trend: In strong downtrends, price stays near lower band
- Catching falling knives: Buying every lower band touch in downtrends
The lower band adapts to volatility just like the upper band. During volatile periods, bands widen to accommodate larger moves; during quiet periods, they narrow, making the bands dynamic support and resistance levels.