Bollinger Bands are a volatility indicator drawn as three lines around price: a moving average in the middle, and one band above and one below. When the market is quiet, the bands tighten. When it gets volatile, they widen. That is the whole idea, and it is why the indicator shows up on almost every charting platform.
The hard part is reading them: touching the upper band is not a sell signal, and touching the lower band is not a buy signal. This guide covers the formula, squeezes, %B, and what changes on leveraged perpetual futures.
This is educational content, not trading advice. Indicators describe past price behavior and do not predict what happens next.
What Bollinger Bands Are
John Bollinger developed the bands in the 1980s. The standard setup uses three lines:
- Middle band: a 20-period simple moving average (SMA) of the closing price.
- Upper band: the middle band plus 2 standard deviations of price over the same 20 periods.
- Lower band: the middle band minus 2 standard deviations.
In formula form:
Middle = SMA(close, 20)
Upper = Middle + 2 × σ
Lower = Middle − 2 × σ
Here σ is the standard deviation of the closing price over the same 20 periods. Standard deviation measures how widely prices scatter around their average. High volatility means a large σ and wide bands. Low volatility means a small σ and narrow bands.
The "20 and 2" values are the commonly used defaults, not a law. John Bollinger's own rules page describes 20 periods and two standard deviations as default starting points that may need adjusting for a given market. They apply to whatever timeframe your chart uses: on a 4-hour chart, "20 periods" means 20 four-hour candles.
One note on interpretation: the bands are statistical envelopes, not support and resistance levels. They tell you how stretched price is relative to its own recent behavior. They do not tell you where it must turn.
Bandwidth and the Squeeze
Because the band distance is driven by volatility, the gap between the bands carries information on its own. A common measure is bandwidth:
Bandwidth = (Upper − Lower) / Middle
Dividing by the middle band makes the number comparable across different price levels and different assets.
A squeeze is a period where bandwidth is unusually low compared with its own recent history. Volatility tends to move in cycles, so traders often treat a squeeze as a sign that the market is compressed and may expand again. Two cautions apply:
- A squeeze says volatility is low. It does not say which direction the next move goes.
- "Low" is relative. There is no universal bandwidth number that defines a squeeze, so compare the current reading against that chart's own history.
Many traders wait for a close outside a band after a squeeze and confirm with another tool. Early breaks can still reverse (a "false breakout"), so a squeeze is a reason to pay attention, not a trade on its own.
%B: Where Price Sits Inside the Bands
%B turns the picture into a single number:
%B = (Price − Lower) / (Upper − Lower)
- %B = 1.0: price is at the upper band.
- %B = 0.5: price is at the middle band.
- %B = 0.0: price is at the lower band.
- Above 1.0 or below 0.0: price is outside the bands.
This helps with scanning charts or building alerts. It is still just a position reading: a %B above 1.0 means price is extended relative to its 20-period behavior. It can occur during a continuing trend and does not, by itself, identify a reversal.
How Traders Read the Bands
There are two broad approaches, and they point in opposite directions.
Mean reversion. In a ranging market, price often drifts back toward the middle band after stretching to an outer one. Traders using this view look for price to return toward the average after touching a band.
Breakout and trend following. In a trending market, price can close outside the bands repeatedly. This is often called walking the band: in a strong uptrend, candles can hug the upper band for a long time while the middle band slopes up. A mean-reversion trader who sells every upper-band touch in that situation keeps fading a move that keeps going.
This is why a band touch alone is not a signal. The same touch means different things depending on the regime:
| Context | What a band touch may suggest |
|---|---|
| Sideways range, flat middle band | Price may be stretched and could revert |
| Strong trend, middle band sloping | Price may simply be trending, with more room to run |
| Right after a squeeze | Volatility may be expanding, so direction is still unconfirmed |
Before leaning on a touch, check what the middle band is doing and whether the market is ranging or trending.
Combining Bollinger Bands With Other Tools
Bollinger Bands measure one thing: price relative to recent volatility. Most traders pair them with something that measures a different thing.
- Volume. A band break on rising volume is generally read as stronger participation than one on thin volume. Neither guarantees follow-through.
- RSI. The Relative Strength Index measures momentum. If price pushes outside a band while momentum is fading, some traders treat that as a warning that the move is tiring. If momentum is strong and rising, it supports a trend reading. Disagreement between the two tools is information; agreement is not proof.
- Market structure. Prior highs, lows, and ranges often matter more than the bands themselves.
Each added tool should answer a question the bands cannot, not just agree with you.
Parameter Notes for 24/7 Crypto Markets
The 20-period, 2-deviation defaults date from an era of equity markets with set trading hours. Crypto trades continuously, and daily candle boundaries depend on the chart's time zone.
Common adjustments include using a different period, or widening the multiplier above 2 so that fewer candles register as "outside the bands." We have no evidence that any particular non-default setting is superior.
The default settings are a starting point; alternatives should be tested for the asset and timeframe you trade. On lower timeframes, short-term fluctuations can make signals harder to interpret. Whatever you choose, keep it consistent.
Using Bollinger Bands on Perpetual Futures
Everything above applies to spot charts and perp charts alike. What changes on perpetuals is the cost of being wrong.
Leverage amplifies band-walk losses. If you short an upper-band touch with leverage and price keeps walking the band, losses can consume your margin and bring the position closer to liquidation. See What Is Leverage Trading in Crypto? and How Liquidations Work on LeverUp for the mechanics.
Add positioning context. A squeeze tells you volatility is compressed; it does not tell you who is crowded. Funding rates and open interest add a second view. Rising open interest only tells you that outstanding contracts are increasing; on its own it does not show which side is crowded or how a squeeze will resolve. See What Is Funding Rate in Crypto? and What Is Open Interest in Crypto?. These are context, not triggers.
Decide your stop before you enter. Bands expand when volatility rises, so a stop placed a fixed distance away can sit inside normal noise. Some traders place stops relative to the middle band or beyond a recent swing, and size the position so that a stop-out is survivable. For sizing and discipline, see Risk Management for New Traders on LeverUp.
Know which price your platform uses. Check the price series used by your chart and the price reference used for liquidation. They may differ, so a band touch alone does not establish how close a position is to liquidation. See Mark Price vs. Last Price.
Account for slippage. Breakouts happen in fast markets, when fills can drift from expectations. See What Is Slippage in DeFi?.
Common Mistakes
- Fading a trend. Selling every upper-band touch in a strong uptrend, or buying every lower-band touch in a downtrend, is the classic walking-the-band mistake.
- Assuming a squeeze has a direction. It shows compression, not bias.
- Over-tuning settings. Fitting parameters to recent data describes the past, not the future.
- Skipping the stop. With leverage, "it will come back to the middle band" is not a risk plan.
FAQ
What do Bollinger Bands tell you? How far price is from its 20-period average, in units of recent volatility.
Is touching the upper Bollinger Band a sell signal? No. In a range it may precede a move back to the middle band, but in a strong trend price can stay at the upper band for a long time.
What is a Bollinger Band squeeze? A period when bandwidth is low relative to its own recent history, meaning volatility has compressed. It suggests the market could expand but does not indicate the direction.
Trading perpetuals involves substantial risk, including the loss of your full margin. Never trade with funds you cannot afford to lose.
To put a plan into practice, see How to Open Your First Trade on LeverUp and How to Set Stop Loss and Take Profit on LeverUp.
Trade on LeverUp: app.leverup.xyz