3.4 Volatility Indicators

Master volatility-based indicators — Bollinger Bands, ATR, Keltner Channels, Donchian Channels. ATR is the most underrated indicator in trading.

Layer 3: Technical Indicators — Chapter 4 Goal: Master volatility-based indicators — Bollinger Bands, ATR, Keltner Channels, Donchian Channels. ATR is the most underrated indicator in trading.

The Core Idea

Volatility indicators measure the size and consistency of price moves. Not direction — magnitude.

Volatility matters because:

It dictates how much room you need to give a trade (stop loss placement)
It tells you when trends are about to start or end
It identifies "compression" before breakouts
It determines appropriate position size

ATR (Average True Range) is the single most useful volatility indicator for swing traders. Master it.

Bollinger Bands

Developed by John Bollinger in the 1980s. The most popular volatility indicator.

What They Are

Three lines drawn on the price chart:

Middle Band: 20-period SMA
Upper Band: Middle + 2 standard deviations
Lower Band: Middle - 2 standard deviations

Formula

Middle Band = 20-period SMA
Upper Band = Middle Band + (2 × σ)
Lower Band = Middle Band - (2 × σ)

Where σ = standard deviation of price over 20 periods

Why 20 and 2σ?

20-period = ~1 month
2 standard deviations = ~95% of price action (statistically)
These defaults work; tweaking rarely improves things

How to Read Bollinger Bands

Band Width

Wide bands = high volatility
Narrow bands = low volatility ("squeeze")

Price Relative to Bands

Touching upper band = price is "extended" (high)
Touching lower band = price is "extended" (low)
Riding the upper band in uptrend = strong momentum
Riding the lower band in downtrend = strong momentum

Common Misuse

"Price touched upper band → sell."

In strong trends, price can ride the upper band for weeks. Don't fade extreme readings in trends. Sound familiar? Same lesson as RSI overbought.

The Bollinger Squeeze

This is the most actionable Bollinger Band pattern.

What It Looks Like

Bands contract dramatically (low volatility)
Price trades in a tight range
Often accompanied by decreasing volume

Why It Matters

Low volatility precedes high volatility. Markets that are quiet won't stay quiet. A squeeze is "loading the spring" for a breakout.

Trading the Squeeze

Identify a squeeze (bands tighter than usual for that stock)
Wait for the breakout direction (price closing outside one band)
Enter in the direction of the break with volume confirmation
Stop: just inside the band on the other side
Target: previous swing extremes, or 2× ATR

Bollinger Band Expansion

When bands rapidly expand:

A trend has started (often after a squeeze)
Ride the band that price is trending along
Don't fade until clear reversal signal

Bollinger Band Walking

"Walking the Band"

In a strong uptrend, price hugs the upper band for many bars
Each touch of the upper band is a continuation signal, not a reversal
Same for downtrends and the lower band

Recognition

3+ consecutive closes near the upper band = trend established
Pullbacks return to the middle band (20 SMA), not below
Strong, durable trend

ATR: Average True Range

Also from J. Welles Wilder. The most underrated indicator in trading.

What It Measures

The average price movement (range) over the past N periods. Pure volatility measurement.

Formula

First, calculate True Range (TR) for each period:

TR = max(
    High - Low,
    |High - Previous Close|,
    |Low - Previous Close|
)

(The max handles gap days correctly.)

Then average over N periods:

ATR = N-period average of TR

Default: 14 periods.

Output

A single number in price units. E.g., "ATR(14) = $4.50" means AMD's average daily range has been $4.50.

Why ATR Is So Important

1. Stop Loss Placement

Stop = Entry - (1.5 to 3) × ATR

This places your stop outside normal noise, so you don't get whipsawed.

Example: AMD ATR = $4. Enter long at $200. Stop at $200 - 2×$4 = $192. This stop respects AMD's normal daily noise.

2. Position Sizing

Risk per share = your stop distance. ATR-based stops give you a volatility-adjusted risk.

For volatile stocks (high ATR), use smaller positions to keep $ risk constant.

Position Size = Risk Amount / (ATR-based Stop Distance)

3. Profit Targets

Target = Entry + 2-3 × ATR for a conservative trade. Target = Entry + 5-10 × ATR for a swing.

4. Comparing Stocks

ATR lets you compare apples to apples:

AMD: $200, ATR = $4 → 2% daily range
TSLA: $200, ATR = $8 → 4% daily range (twice as volatile)

For a given account risk, you can hold half as many TSLA shares.

5. Detecting Regime Shifts

ATR rising = volatility expanding (often trend starting or accelerating)
ATR falling = volatility contracting (consolidation, breakout coming)

ATR-Based Trailing Stops

Powerful technique used by pros.

The Mechanic

Initial stop: Entry - 2 × ATR
As price rises, recalculate: New stop = Current Price - 2 × ATR
Stop only moves UP, never down

Why It Works

Adapts to current volatility
Doesn't get whipsawed by normal noise
Gives winners room to breathe

Practical Variants

Chandelier Exit: Stop = (Highest High since entry) - 3 × ATR
Supertrend indicator: A pre-built ATR-based trailing stop indicator

Keltner Channels

Similar to Bollinger Bands but ATR-based instead of standard deviation-based.

Formula

Middle Line = 20-period EMA
Upper Channel = Middle + (2 × ATR)
Lower Channel = Middle - (2 × ATR)

Differences from Bollinger Bands

Uses ATR for width (Bollinger uses standard deviation)
More stable, less reactive to short-term price spikes
Some traders prefer for trend trading

Use Case

Trend following with cleaner signals than Bollinger
Less common but valid alternative

Recommendation: Pick one (Bollinger OR Keltner), not both. Most traders use Bollinger.

Donchian Channels

Developed by Richard Donchian (the "Turtle Trader" mentor).

What It Is

Upper Channel = Highest High over N periods
Lower Channel = Lowest Low over N periods
Middle Line = (Upper + Lower) / 2

Default N: 20.

What It Shows

The recent extremes in price — pure range, not volatility-adjusted.

Famous Strategy: Donchian Breakout

Enter long when price closes above 20-day high
Enter short when price closes below 20-day low
Exit when price hits opposite Donchian band

This was the basis of the Turtle Trading System. Simple, mechanical, profitable for decades.

Use For Swing Trading

Identify breakouts from recent ranges
Identify when to take profits (price hits opposite band)
Combine with volume confirmation

Comparing the Volatility Indicators

Indicator	Best For	Skip If
Bollinger Bands	Range trading, squeeze setups	You're trend-following only
ATR	Stop placement, position sizing	Never skip ATR
Keltner Channels	Trend trading with bands	Already using Bollinger
Donchian Channels	Pure breakout systems	You prefer subjective levels

ATR = average miles per hour (typical movement)
Bollinger Bands = the lanes of the highway (where price usually stays)
Bollinger Squeeze = traffic slowing down (rest stop before highway opens up)
Donchian Channels = the highest and lowest mileposts you've passed recently

Practical Setup

For swing trading on daily chart:

Don't Stack

Multiple band systems on one chart
ATR + standard deviation indicators (redundant)
Too many indicators in any category

Practical Takeaways

ATR is the most important volatility indicator. Use it for stops, sizing, and targets.
ATR-based stops adapt to current market conditions. Adjust your position size accordingly.
Bollinger Bands measure standard deviation. Touching them isn't a buy/sell signal — context matters.
The Bollinger Squeeze precedes breakouts. Watch for tight bands + volume buildup.
In strong trends, price "walks the band." Don't fade it.
Pick one band system (Bollinger or Keltner). Don't stack.
Donchian Channels are excellent for mechanical breakout strategies.

Quick Self-Check

Before moving to 3.5, you should be able to answer:

What are the three lines of Bollinger Bands?
What is a "Bollinger Squeeze" and what does it typically precede?
What is the formula for True Range?
How would you use ATR to set a stop loss?
What's the difference between Bollinger Bands and Keltner Channels?
What is the Donchian Channel breakout system?
Why should position size be adjusted based on ATR?

Previous: 3.3 Trend-Following Indicators Next: 3.5 Volume-Based Indicators