ATR

Introduction

Bollinger Bands show volatility as an envelope you read by eye. Sometimes, though, you want volatility as a plain number — one figure that says "a normal move for this market, right now, is about this big." That is exactly what ATR, the Average True Range, provides. It is the most direct volatility measure in common use, and although it began life in commodities (introduced by Welles Wilder, the same analyst behind RSI), it is applied to every market today.

ATR's value is its bluntness. It does not try to tell you where price is going — only how much it tends to move. And knowing the size of a normal move turns out to be one of the most practically useful things in all of technical analysis, especially for managing risk.

True Range: More Than High Minus Low

The obvious way to measure a period's movement is its high minus its low. ATR refines this with the idea of true range, which fixes a blind spot: gaps. If a market closes at 100 and opens the next session at 95 (a gap down) before trading in a tight 95–96 range, the plain high-minus-low (just 1) badly understates how much it actually moved — it leapt 5 from the prior close.

True range captures that by taking the greatest of three distances:

By including the previous close, true range counts any overnight gap as part of the move. It is the honest measure of how far price travelled, not just how far it ranged within the session.

Averaging It: ATR

A single period's true range is noisy. ATR smooths it by averaging true range over a lookback window — conventionally 14 periods (Wilder's smoothing). The result is a steady line that rises when ranges are expanding and falls when they are contracting.

That last point is the whole character of ATR: in the volatile stretch the line rises during both the up-moves and the down-moves, because it does not care which way price went — only how far.

How ATR Is Used

1. Defining a "normal move." ATR gives you a yardstick. If a market's ATR is 2, then a 2-point move is unremarkable and a 6-point move is three times the normal daily range — genuinely large. This calibration stops you from over-reacting to ordinary noise or under-reacting to a real expansion.

2. Scaling stops to volatility. This is ATR's most important practical use, and it links directly to risk management. A protective stop placed a fixed distance from price ignores how much the market actually moves — too tight in a volatile market (you get knocked out by noise), too loose in a calm one. Placing a stop a multiple of ATR away (say 2 × ATR) scales the buffer to current volatility: wide when the market is wild, tight when it is calm. The principle: give a position room proportional to how much the market normally moves.

3. Sizing positions. The same logic extends to how much to hold. If risk is defined as ATR-based stop distance, a more volatile market (larger ATR) implies a smaller position for the same risk, and a calmer one a larger position. ATR turns "how volatile is this?" into a number you can size against. (These ideas are developed fully in the Risk Management topics — Position Sizing and Stop Losses.)

Comparing Across Markets

One subtlety: ATR is expressed in the instrument's own price units, so raw ATR values are not comparable across markets. A share trading near 1,000 will have a far larger ATR than one near 10 simply because its prices are bigger — not because it is "more volatile" in any meaningful sense. To compare fairly, analysts often express ATR relative to price (for example, ATR as a percentage of price). A 1% ATR is a 1% ATR whether the instrument costs 10 or 1,000.

A Worked Example

A share has an ATR of about 1.5, and has done for weeks — calm, orderly. An analyst describes a normal day as "roughly a 1.5 range." A protective stop using 2 × ATR would sit about 3 away from price — far enough that ordinary daily noise won't trip it.

Then news hits and the market moves sharply; over a week the ATR climbs to 4. Nothing about direction is implied — ATR rose the same whether the move was up or down — but the character has changed: a normal day is now a 4 range, almost three times before. The same 2 × ATR stop now needs about 8 of room, and a volatility-aware participant would reduce position size accordingly to keep risk steady. ATR has done its one job: told you, in a number, how big "normal" has become.

The Honest Limits

• ATR measures size, never direction. A high ATR accompanies sharp rallies and sharp crashes alike. It will never tell you which way price is going.
• Raw ATR isn't comparable across instruments. It is in price units; normalise to price (e.g. a percentage) for fair comparison.
• It is descriptive and lagging. ATR is an average of ranges that already happened. It tells you what volatility has been — a sound basis for sizing risk, not a forecast of the next move.

ATR distils volatility to a single, practical number — the backbone of volatility-aware risk management. With trend, momentum, volume, and volatility now covered, the final indicator article steps up to a complete system that tries to combine several of these at once: the Ichimoku Cloud.