What are Bollinger Bands? Definition, build & key trading signals
What are Bollinger Bands?
Bollinger Bands are a popular chart indicator created by John Bollinger. They consist of three lines plotted on a price chart:
- A middle band: a simple moving average (SMA).
- An upper band: the SMA plus a set number of standard deviations.
- A lower band: the SMA minus the same number of standard deviations.
These bands expand and contract based on market volatility. Prices near the upper band suggest the asset might be overbought, while prices near the lower band suggest it could be oversold.
In short: they give you a visual gauge of volatility and potential trend changes.
How it works
Here's how Bollinger Bands function in practice:
- Choose your settings: Most traders use a 20-period SMA and 2 standard deviations.
- Bands adjust to volatility: In high-volatility markets, the bands widen; in low-volatility markets, they narrow.
- Identify price position: If price touches the upper band, it may signal overbought conditions; the lower band may signal oversold conditions.
- Watch for breakouts: A strong price move outside the bands can signal a potential trend continuation or reversal.
Why use Bollinger Bands?
They're useful when you:
- Want to measure market volatility visually.
- Need to spot potential reversal points.
- Are looking for breakout opportunities.
- Want to combine them with other indicators for confirmation.
Bollinger Bands vs Moving Averages
Here's a quick side-by-side:
| Feature | Bollinger Bands | Moving Average Only |
|---|---|---|
| Volatility measurement | Yes, adjusts width based on standard deviation | No, single line based on price average |
| Price context | Shows relatively high/low levels | Shows trend direction only |
| Trading signals | Potential overbought/oversold + breakouts | Trend-following only |
Use Bollinger Bands when you want volatility + trend insights. Use a moving average when you just need trend direction.
Common uses and strategies
- Bollinger Bounce: Trade reversals when price hits an outer band and moves back toward the middle.
- Bollinger Squeeze: Watch for narrow bands signaling upcoming volatility spikes.
- Trend confirmation: Combine with RSI or MACD for more accurate entries/exits.
FAQs
- Do Bollinger Bands work in all markets?: Yes — they can be applied to stocks, forex, crypto, and commodities.
- What's the best setting for crypto trading?: Many traders use the default (20-period SMA, 2 standard deviations) but tweak for faster or slower signals.
- Are Bollinger Bands accurate for predicting price?: They don't predict exact prices but help assess market conditions and potential setups.