Acceleration Bands: Width From the Bar

Michael Whitman · Trading since 2017, full-time since 2020 · Reviewed 2026-09-06

Acceleration Bands place an envelope around a moving average using each bar's own high-low range as the scaling factor rather than the standard deviation of closes. The result reacts to a change in bar width one bar sooner than a deviation-based band does.

How it works

A candlestick chart of the site's shared price history. The headline on the chart reads: Bands set by the width of each bar, not by deviation. — Bands set by the width of each bar, not by deviation. Illustrative chart - not real market data.

Acceleration Bands wrap an envelope around a moving average. What makes them their own indicator is where the width comes from — each bar’s own high and low, not the spread of closing prices.

A gently rising stretch of the long price series. The headline on the chart reads: High and low scaled by the bar's own range, then smoothed. — High and low scaled by the bar's own range, then smoothed. Illustrative chart - not real market data.

Each bar’s high is scaled up and its low scaled down by a factor derived from the bar’s range relative to its midpoint, and those scaled values are then smoothed into the upper and lower bands.

A calmly advancing stretch of the long price series. The headline on the chart reads: Which makes them react faster than a deviation band. — Which makes them react faster than a deviation band. Illustrative chart - not real market data.

The practical difference is timing. A Bollinger Band widens only after the larger closes have entered its deviation window; a range-scaled band widens on the bar that was wide.

What it is used for

A choppy, directionless stretch of the long price series. The headline on the chart reads: The published use is a breakout that holds for two bars. — The published use is a breakout that holds for two bars. Illustrative chart - not real market data.

The rule as published is a two-bar confirmation. Price closing outside the upper band for two consecutive bars is treated as the start of a move rather than a single excursion.

A flat, quiet stretch of the long price series. The headline on the chart reads: Band width is a volatility reading in disguise. — Band width is a volatility reading in disguise. Illustrative chart - not real market data.

The width itself is the more useful output. Any envelope’s separation is a volatility measurement, and reading it directly is often more informative than watching for touches.

A strongly rising stretch of the long price series. The headline on the chart reads: Average true range here spans 0.28 to 0.80 across the series. — Average true range here spans 0.28 to 0.80 across the series. Illustrative chart - not real market data.

On this site’s shared 576-bar history the 14-bar average true range runs from 0.2823 at the tenth percentile to 0.7954 at the ninetieth — a ratio of 2.82 between quiet and active conditions.

A declining stretch of the long price series. The headline on the chart reads: So any fixed-width band is wrong most of the time. — So any fixed-width band is wrong most of the time. Illustrative chart - not real market data.

That spread is the argument for adaptive bands of any kind. A fixed-percentage envelope set for the middle of that range is materially too tight in the top decile and too loose in the bottom one, and it is in one of those two states most of the time.

In practice

A candlestick chart with a volume histogram beneath it, with the volume histogram emphasised. The headline on the chart reads: The bands see price width and nothing else. — The bands see price width and nothing else. Illustrative chart - not real market data.

Nothing in the calculation reads volume. A wide bar on no participation widens the bands exactly as much as one on heavy trading, and only one of those is a genuine expansion.

A long-horizon candlestick view of the same price series. The headline on the chart reads: On a slower chart the same setting is a different tool. — On a slower chart the same setting is a different tool. Illustrative chart - not real market data.

The smoothing length is measured in bars, so a 20-period setting on a five-minute chart and on a daily chart are completely different instruments with one label.

A candlestick series containing several opening gaps, with the largest opening gap marked. The headline on the chart reads: A gap widens them a bar after it would have helped. — A gap widens them a bar after it would have helped. Illustrative chart - not real market data.

A gap is the one case a range-based band handles badly. The gap itself is not inside any bar’s high-low range, so the bands widen only once a wide bar prints — after the event.

A declining stretch of the long price series, with the entry price and the level at which a stop would trigger drawn as horizontal lines. The headline on the chart reads: The lower band is a common and very loose stop. — The lower band is a common and very loose stop. Illustrative chart - not real market data.

Using the opposite band as a stop is common and very loose. It is a wide exit that needs a correspondingly small position size, and that adjustment is the part usually left out.

And every band touch traded costs a share of a bar. Illustrative chart - not real market data.

Band-touch systems are high turnover. Each trade is a round trip at 2% of a median bar’s range on this history, and touches are frequent by construction.

A 72-bar candlestick section of the shared price history. The headline on the chart reads: The band is a computed line with no orders at it. — The band is a computed line with no orders at it. Illustrative chart - not real market data.

No participant is defending a band. Unlike a prior high, the level is arithmetic — which is the reason a touch alone has never been a sufficient signal in any envelope system.

How it sits in the envelope family

Three envelopes cover almost every variation and they differ only in what sets the width. Bollinger Bands use the standard deviation of closes. Keltner Channels use the average true range. Acceleration Bands use each bar’s own high-low range scaled by its midpoint.

Those three inputs disagree most in exactly the conditions that matter. Deviation of closes stays narrow through a session of wide bars that all close in the same place; a range-based measure does not. Knowing which input your envelope uses explains its behaviour better than any parameter, and it is the first question to ask about any band you have not built yourself.

One more property separates a range-based band from a close-based one, and it shows up on the day it matters. A session of very wide bars that all close near the same level produces almost no deviation of closes and a large amount of range. The deviation band stays narrow through it; the range band widens.

Which of those is correct depends entirely on what you are using the band for. For a mean-reversion rule the closes are the relevant series, because that is where price keeps settling. For a stop distance the range is, because that is what price is capable of doing inside a bar.

What acceleration bands are not

They are not Bollinger Bands. Different width input, different behaviour.

They are not a probability. No distribution is assumed or implied.

They are not a signal on their own. The published rule needs two bars.

And they are not adaptive to participation. They read price width only.

When it fails

A sideways, range-bound candlestick series. The headline on the chart reads: In a range price touches both bands and goes nowhere. — In a range price touches both bands and goes nowhere. Illustrative chart - not real market data.

In a range both bands get touched repeatedly and every touch looks like the start of something. A breakout rule applied there produces a steady sequence of round trips against a market that ends the period where it began.

The second failure is the two-bar rule in a fast market. Two closes outside the band can be most of the move, so the confirmation that removes false starts also removes the good entries.

A third is treating a touch as a level. Nothing rests there.

A fourth is running it beside a Bollinger Band as confirmation. Two envelopes computed from overlapping inputs agreeing is not independent evidence.

And a fifth is leaving the smoothing at a default. The length sets how quickly the bands respond, and it deserves the same attention the multiple gets on any other volatility tool.

The original data

On this site’s shared 576-bar history the 14-bar average true range has a median of 0.5994, a tenth percentile of 0.2823 and a ninetieth of 0.7954 — a 2.82-fold spread — and a median 1.22 times the median bar range of 0.4916. Bar ranges themselves span 0.17 to 1.10 between the tenth and ninetieth percentiles. The figures are in research/series-measurements.json, produced by site/measure_series.py.

A 72-bar window of the shared price history, cut short at the decision bar. The headline on the chart reads: Price closed outside the upper band. Buy it? — Price closed outside the upper band. Buy it? Illustrative chart - not real market data.

The 6.5-fold spread in raw bar ranges against the 2.82-fold spread in the smoothed average is worth noticing. Smoothing removes more than half the variation, which is what makes a smoothed band usable and also what makes it late. Decide which of those two properties your method needs before choosing a band — a breakout system wants the responsiveness and a mean-reversion system wants the stability, and no single setting delivers both.

Bollinger Bands are the deviation-based envelope. Keltner Channels use average true range instead. And breakout is the event these bands were built to identify.

What I actually do

I do not run these, and I read the family they belong to constantly. What matters is not which envelope you pick but that you know what sets its width. Deviation bands, range bands and fixed-percentage bands behave differently in exactly the conditions where you most need to trust them.

— Michael Whitman

This page is educational, not financial advice. Test every idea on your own charts before risking money.