Bollinger Bands are one of the most popular technical analysis tools, developed by John Bollinger in the 1980s.
They are designed to measure market volatility and identify potential overbought or oversold conditions.
At their core, Bollinger Bands consist of three lines:
“Volatility is not always your enemy; it’s your signal.” — John Bollinger
When the market becomes more volatile, the bands widen.
When the market becomes less volatile, the bands contract.
This dynamic expansion and contraction help traders visualize when prices might be reaching extremes.
However, these signals should not be used in isolation — always confirm with volume, trend direction, or momentum indicators.
✅ Bollinger Bounce
When price touches one band and “bounces” back toward the opposite one. Often used in range-bound markets.
✅ Bollinger Squeeze
Occurs when the bands narrow significantly, suggesting a period of low volatility that might lead to a breakout.
✅ Band Breakout
Traders look for the price to close outside the bands, interpreting it as the start of a new trend.
You can easily calculate Bollinger Bands using the pandas library:
import pandas as pd# Assume df contains a 'Close' columndf['SMA'] = df['Close'].rolling(window=20).mean()df['STD'] = df['Close'].rolling(window=20).std()df['UpperBand'] = df['SMA'] + (2 * df['STD'])df['LowerBand'] = df['SMA'] - (2 * df['STD'])
This simple script generates upper and lower Bollinger Bands around your price data.
“Markets are like rubber bands — when they stretch too far, they snap back.”
Bollinger Bands are a versatile and adaptive tool.
Whether you’re a day trader or a long-term investor, understanding how prices behave relative to these bands can sharpen your timing, reduce false signals, and boost your confidence in reading the market.

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