Average True Range (ATR): The Volatility Number Behind Every Stop

Most stop-loss conversations end up at the same number. How far away is normal? ATR is the answer people reach for, and it is also one of the most misread indicators on a chart, because the line has no direction. It does not go up when the stock goes up. It goes up when the bars get bigger. This post is the mechanics: what true range is, how Wilder's 14-period smoothing turns it into the line you see, with the arithmetic worked out, and what that line can and cannot tell you.

Quick Answer

Each piece gets its own section, with a worked example you can check by hand.

What Is the ATR Indicator?

ATR answers one question: on this chart, how far does price typically travel per bar? The StockCharts ChartSchool article on Average True Range credits it to J. Welles Wilder and describes it as an indicator that measures volatility. Wikipedia's entry dates it to Wilder's 1978 book New Concepts in Technical Trading Systems and says the indicator gives no indication of price trend, only the degree of price volatility.

On a chart it is a single line in its own pane, usually under the price. In dollars on a stock, in points on an index, in pips on a forex pair. A reading of 0.64 on a $51 stock means the stock has been covering about 64 cents per bar once you count gaps. It is not a signal, it has no overbought line, and it does not cross anything. It is a measurement, which is exactly why other indicators borrow it: Keltner channels and Supertrend are both built on ATR, and the Keltner Channel guide and the Supertrend breakdown cover what each does with it.

True Range: The Three-Way Max

The "true" in the name is the point. The plain range of a bar is high minus low. That misses everything that happened between bars. A stock that closes at $50.50 and opens the next day at $51.50 has moved a dollar before the first trade, and a bar whose high-low is only 60 cents would hide it. Wilder's fix is to take the largest of three distances.

That is the definition as StockCharts gives it. Most bars are an ordinary day and the first leg wins. The other two only matter when price gaps away from the previous close. If the stock gaps up and the whole bar trades above the old close, leg 2 wins. If it gaps down and the whole bar trades below it, leg 3 wins. The worked table below has one of each, so you can see where the max switches.

How ATR Is Calculated, Bar by Bar

Hypothetical numbers, 14 bars plus one. Bar 0 only supplies the first previous close ($50.10), so every row below can use all three legs. For each bar the table shows the three distances and the one that wins.

Look at bar 8. The high-low is $0.60, but the stock closed bar 7 at $50.50 and bar 8 traded no lower than $50.95, so the high minus the previous close is $1.05 and that is the true range. On bar 12 the stock closed the prior bar at $50.95 and the whole bar traded below it, so the low minus the previous close ($0.80) beats the $0.70 high-low. Every other row is plain high minus low.

Turning true range into ATR

The first ATR is a plain average. Add the 14 true ranges from bars 1 to 14: the total is $8.90, and $8.90 / 14 = $0.6357, which rounds to $0.64. (StockCharts describes the first TR as simply high minus low, and the first 14-day ATR as the average of the daily TR values over the last 14 days. Here every row has a previous close, so each uses all three legs.)

From there it is a running average, Wilder's smoothing: current ATR = ((prior ATR x 13) + current TR) / 14. Bar 15 is a wide bar with a true range of $1.20. So ATR(15) = (0.6357 x 13 + 1.20) / 14 = (8.264 + 1.20) / 14 = 9.464 / 14, which is about $0.68. One bar nearly twice the size of the average moved ATR from 0.64 to 0.68, not to 1.20. Each new bar carries a weight of one fourteenth, which is why ATR is smooth, and why it is slow.

How to Read ATR: A Level, Not a Direction

This is the part most people get wrong. StockCharts says it directly: it is important to remember that ATR doesn't indicate price direction, just volatility, and it is not a directional indicator like MACD or RSI. A rising ATR can come from a stock breaking out or a stock breaking down. A falling ATR means ranges are shrinking, which can happen in a drifting uptrend or a dead range.

So the useful read is the level and the change in it, in time. Rising: bars are getting bigger than they were. Falling: smaller. Flat: the current rhythm is steady. That is the whole vocabulary. It does not tell you to buy, sell, or that a move is about to start. If you want a rough idea of whether a chart is compressing or expanding, ATR is one way to see it, and the Bollinger Bands guide shows another through band width.

The period matters the same way it does on any lookback. StockCharts says ATR is typically based on 14 periods, and notes that Wilder often used 8 in his own work. A shorter period follows the current bars more closely and jumps more. A longer one is smoother and slower to notice that the chart changed.

ATR as a Percent of Price

ATR is in price units, and that makes it awkward across stocks. StockCharts is explicit that it is not shown as a percentage of the current close, so low-priced stocks have lower ATR values than high-priced stocks, and the raw values are not comparable. Divide by price to fix it: ATR% = ATR / close x 100.

Hypothetical example. A $5.00 stock with an ATR of $0.20 and a $500.00 stock with an ATR of $2.50. The $500 stock has more than ten times the ATR in dollars. But $0.20 / $5.00 x 100 = 4.0%, and $2.50 / $500.00 x 100 = 0.5%. The cheap stock is eight times as volatile in percentage terms. In the worked example above, ATR(14) of $0.64 on a $50.95 close is 1.25% of price.

Percent matters in two places. When you compare two tickers on a watchlist, and when the same stock has changed a lot in price, because an ATR from when it was $20 is not the same thing as one now that it is $60. If you size by dollars at risk, the position sizing guide covers how the stop distance turns into share count.

ATR on a Quiet Chart vs a Fast One

Same indicator, two very different charts. The diagram below is built from 40 made-up bars: a seed bar, 20 quiet ones, then 19 fast ones. The bottom pane is ATR(14) computed from them.

The table puts numbers on it. Two things stand out. First, ATR lags: the average bar range over the fast stretch is $0.89, but ATR at bar 39 reads $0.74, still catching up, because each new bar only carries a fourteenth of the weight. Second, the percent view makes the change obvious: ATR went from 0.45% of price on the quiet stretch to 1.32% on the fast one, roughly three times.

The last row is the whole reason traders watch it. A 50 cent stop is about two ATRs on the quiet stretch, a lot of room. On the fast stretch the same 50 cents is less than one ATR, which is inside a normal bar. Nothing about the stop changed. The chart did. That is also why a number you used last week can be wrong this week.

ATR Indicator Stop Loss: The Short Version

People mostly use ATR to size the distance of a stop: entry minus some multiple of ATR for a long, so the stop sits outside the noise of a normal bar. That is the whole idea, and it is general knowledge rather than a rule from any one source. The multiple is a choice you make. There is no number the indicator hands you, and a stop that is only an ATR multiple can still land in the middle of nothing, with no structure behind it.

Where the stop goes relative to structure, how to pick between a structure stop and a volatility stop, and a worked example are all in the AI stop loss placement guide, so this post does not repeat them. The risk side, how much to lose per trade before the stop even matters, is in the day trading risk management rules.

ATR and the Screenshot: What SnapPChart Does

The precise version, since this is easy to oversell. SnapPChart reads one chart screenshot you upload. It never calculates ATR and it never picks an ATR multiple for a stop. If you plot ATR under the chart before you take the screenshot, the line is in the image like everything else, but nothing in the grader's instructions tells it to read it. Those instructions name EMAs, VWAP, MACD and volume, plus structure and levels.

What you get is a setup grade for a momentum continuation, with an entry, a stop and the reasoning behind that stop's level, targets and the reward-to-risk they imply. It takes continuation setups only, a pullback in an established uptrend or a rally in an established downtrend, and it does not take reversals. So ATR stays yours: check the stop distance it gives you against your own ATR(14) on that timeframe, and decide whether it holds up. What a single image carries is described on the AI chart analysis page, and the broader question of which indicators earn space on an intraday chart is in the indicator roundup for day traders.