ATR vs Standard Deviation
Average true range measures the typical size of a bar, including any gap from the previous close, so it captures everything price did within that bar. Standard deviation instead measures how dispersed closing prices have been, which ignores wicks and gaps entirely.
Two measures of how much a market moves. One looks at the whole bar and the jump from the previous close; the other looks only at where bars closed. That is a bigger difference than it sounds.
What each one is
Average true range measures the typical size of a bar, taking the largest of the bar’s own range and its distance from the previous close. Average true range covers it.
Standard deviation measures dispersion of closes. It reports how spread out recent closing prices have been around their own average. Standard deviation covers it.
One includes gaps and wicks; the other does not. That single design choice decides which questions each can answer.
Where they differ
What each can see. A day that swung widely and closed flat is a large reading on one and almost nothing on the other, because only one of them looks inside the bar.
How gaps are handled. Average true range explicitly includes the jump from the previous close. Standard deviation of closes treats a gap as an ordinary change in level.
How outliers behave. Dispersion is defined by extremes, so one violent close moves it a great deal. Range is an average of bar sizes and absorbs a single event more gently.
What each is normally used for. Stops and position sizing on one side; statistical filters and envelope construction on the other.
Where they agree
Both measure movement rather than direction. Neither has an opinion about which way price is going, which is why both are used as inputs rather than as signals.
Both are backward-looking. Every value comes from bars that have already printed, and neither anticipates a change in conditions.
Both need a length. The lookback decides how quickly the reading responds, and a value chosen for one instrument does not transfer to another.
And both are inputs, not methods. What matters is what you do with the number, which is a separate decision entirely.
Which one to use
Use average true range for stops and sizing. A stop has to survive the full bar including the gap, which is precisely what this measure reports.
Use standard deviation when the question is statistical. Comparing dispersion, building an envelope or filtering on how unusual a close is are all jobs it was designed for.
Use average true range on anything that gaps. Instruments that open away from the previous close leave one measure blind to a large part of their movement.
And when you are not sure which, use average true range. The questions most traders are asking — where to put a stop, how large a position should be — are range questions.
Why the gap is the deciding detail
Because a stop can be jumped. Price that opens beyond your level fills you wherever it can, and only one of these measures counts that possibility at all.
And because wide bars that close flat are common. On this site’s shared series the ninetieth percentile bar range is 1.101 against a median of 0.493, and the largest single bar range was 2.338 — movement a close-based measure substantially understates.
What the measured figures look like here
Average true range over fourteen bars has a median of 0.5994 on this site’s shared series, with a ninetieth percentile of 0.7954.
Bar ranges themselves are wider. Median 0.493, ninetieth percentile 1.101, largest 2.338 — the average smooths a distribution with a long tail.
Trailing stops sized from it survive predictably. At 1, 2, 3 and 4 average ranges the median survival was 3, 10, 22 and 32 bars across 562 trials.
And that spread is the actual choice. A wider stop lasts longer and costs more when it goes, which is a trade-off you can size from a number rather than guess at.
What to check before using either
The lookback length. It decides how quickly the reading responds and it is the only parameter either measure has.
Whether your instrument gaps. If it does, a close-based measure is missing a meaningful share of the movement.
Whether you need comparability. Raw values are in price units, so dividing by price is what makes readings transferable between markets.
And what the number is for. A stop, a size, a filter or an envelope are four different jobs, and only some of them suit each measure.
The original data
Of the 24,971 unique videos in research/search-study-corpus.jsonl, no title compares these two
directly, and only 1 names standard deviation at all — this pair is constructed from subjects the
corpus covers very unevenly. Separately, average true range appears in 307 titles at a median of 9,432
across 220 channels. The counts come from site/corpus_count.py.
307 videos on one and 1 on the other. The range measure is widely taught and the statistical one is essentially absent, despite the latter sitting underneath one of the most popular indicators on the platform.
The answer to the question on that chart is that they are measuring different things. Range says the market moved a lot; dispersion says the closes did not — and for a stop, the first is the relevant fact.
When it fails
The failure is sizing a stop from a close-based measure on an instrument that gaps. The dispersion reading is low because closes have been steady, so the stop is placed close to price. The instrument then opens beyond it, the fill happens wherever liquidity allows, and the loss is larger than the stop suggested. The measure was accurate about closes and silent about the thing that actually mattered.
The second failure is comparing raw values across instruments. They are in price units.
A third is treating either as a direction signal. Both measure movement only.
A fourth is changing the lookback after a losing run. That is fitting.
A fifth is assuming a low reading means safety. It means recent bars were small.
And a sixth is using a fixed distance instead of either. The instrument decides the scale.
Related
Average true range covers the whole-bar measure. Standard deviation covers the close-based one. And the ATR trailing stop covers the most common use of the first.
If you are sizing a stop, you care about how far price can travel within a bar, gap included. That is exactly what average true range measures and exactly what a close-based statistic cannot see. It is not a preference, it is a different question.
— Michael Whitman
This page is educational, not financial advice. Test every idea on your own charts before risking money.