# Accelerator Oscillator A Momentum & Oscillators concept (Classic single-name oscillators) in the LuxAlgo Library, with 1 indicator implementation. ## What is the Accelerator Oscillator? The Accelerator Oscillator (AC) is Bill Williams' measure of momentum's acceleration. It takes the Awesome Oscillator (the 5-period simple moving average of median price minus the 34-period one) and subtracts a 5-period simple moving average of that oscillator from it. What remains is the change in the driving force rather than the force itself. Williams' premise: price is the last thing to change, [momentum](https://www.luxalgo.com/library/concept/momentum/) changes before price, and acceleration changes before momentum, so AC is meant to turn earliest of the three. AC plots as a zero-centered histogram, conventionally colored by whether each bar is higher or lower than the previous one. Rising bars above zero read as accelerating upside pressure; falling bars below zero as accelerating downside pressure. Because it is built entirely from moving averages of median price, it remains a smoothed, lagging statistic: a single color flip is common noise, not proof of a turn. Williams introduced the Accelerator alongside the Awesome Oscillator in New Trading Dimensions (1998), extending the Profitunity method begun in Trading Chaos (1995); there it sits beside the Alligator and fractal breakouts as one input in a checklist rather than a standalone system. The design leans on a driving metaphor: momentum is the market's speed, AC the change in that speed, the foot easing off the accelerator before the car visibly slows. Metaphor aside, the arithmetic is just an oscillator minus its own signal average. Williams' entry rules are deliberately asymmetric around zero: a buy with AC above the zero line requires two consecutive rising columns, a buy from below zero requires three, and sells mirror this, the extra column compensating for trading against the indicated regime. The limits are plain too: everything is an average of past median prices, so the acceleration it reports arrives with lag, and the output is unbounded, price-scaled, without fixed [overbought or oversold](https://www.luxalgo.com/library/concept/overbought-oversold/) levels, and prone to whipsaw in flat markets. ## How to read the Accelerator Oscillator on a chart AC is read from column-to-column change, the zero line, and divergence, in that order. 1. Note the zero line first: columns above zero indicate acceleration favoring the bulls, columns below zero acceleration favoring the bears. 2. Read color as comparison, not sign: a column is green when higher than the previous column and red when lower, so a green column can print below zero and a red one above it. 3. Track runs, not single bars: two or more consecutive columns in one direction is the minimum Williams' rules act on; one flip is routine noise. 4. At fresh price extremes, compare the new AC peak with the prior one: a smaller peak against a more extreme price is the deceleration warning that precedes many turns, though not all. ## How it's calculated Bill Williams' histogram measuring whether momentum, taken as the Awesome Oscillator, is accelerating or decelerating. ``` MP_t = (H_t + L_t) / 2 AO_t = SMA_5(MP)_t - SMA_34(MP)_t AC_t = AO_t - SMA_5(AO)_t SMA_n(x)_t = (1 / n) × Σ_(i=0..n-1) x_(t-i) H_t: high of bar t L_t: low of bar t MP_t: median price of bar t AO_t: Awesome Oscillator at bar t AC_t: Accelerator Oscillator at bar t SMA_n(x)_t: n-bar simple moving average of series x at bar t x: series being averaged, MP for AO and AO for the AC step (x_(t-i) is its value i bars earlier) n: averaging length (5 and 34, fixed in the standard definition) i: bar offset within the averaging window t: bar index ``` Bill Williams' definition fixes the 5 and 34 bar lengths; platforms rarely expose them as inputs. AC is the gap between AO and its own 5-bar average, so it typically turns before AO itself. Plotted as a histogram colored by bar-to-bar change: green when AC_t > AC_(t-1), red when lower. ## How traders use it - As a permission filter over directional entries: Williams' rules require consecutive rising bars before a buy and consecutive falling bars before a sell, and demand an extra confirming bar when the trade is taken from the wrong side of the zero line. - As a deceleration warning: shrinking bars while price grinds to fresh highs or lows show the move's force fading, often ahead of a turn in the Awesome Oscillator itself. - As a divergence tool: [regular divergences](https://www.luxalgo.com/library/concept/regular-bullish-bearish-divergence/) between AC extremes and price extremes are used to anticipate exhaustion, normally with structural confirmation before acting. - As a throttle over other systems: some traders only take longs while AC is rising or above zero, letting the acceleration read veto entries from structure, [MACD](https://www.luxalgo.com/library/concept/macd/), or moving-average setups. - Alongside bounded oscillators: because AC has no fixed scale, pairing it with [RSI](https://www.luxalgo.com/library/concept/rsi/) or the [Stochastic Oscillator](https://www.luxalgo.com/library/concept/stochastic-oscillator/) supplies the overbought and oversold context AC cannot provide. ## Accelerator Oscillator vs other momentum tools - **MACD** (https://www.luxalgo.com/library/concept/macd/): The MACD histogram plots the MACD line minus its signal line, the same trick AC performs on the Awesome Oscillator: a momentum measure minus its own average. The difference is the inputs, EMAs of the close there, SMAs of the bar midpoint here. - **Momentum** (https://www.luxalgo.com/library/concept/momentum/): Momentum measures the change in price over a lookback, a first derivative. AC sits one derivative higher, tracking whether that force is growing or fading, earlier in principle and noisier in practice. - **RSI** (https://www.luxalgo.com/library/concept/rsi/): RSI is bounded between 0 and 100 and read against fixed thresholds, which suits mean-reversion framing. AC is unbounded, read only against its own recent columns and the zero line, which suits regime and timing filters. ## FAQ ### How is the Accelerator Oscillator different from the Awesome Oscillator? The Awesome Oscillator measures momentum as the spread between 5-period and 34-period averages of median price. The Accelerator Oscillator subtracts a 5-period average of the Awesome Oscillator from the Awesome Oscillator itself, so it measures how that momentum is changing. AC therefore tends to turn earlier but is noisier; a common division of labor is AC for deceleration warnings, AO for underlying momentum direction. ### Is a color change on the Accelerator Oscillator a buy or sell signal? Not on its own. Single rising or falling bars appear constantly inside noise. Williams' rules require consecutive bars in the new direction and add an extra required bar when the reading sits on the opposite side of zero from the intended trade. In practice AC works as a filter alongside structure or trend tools rather than as a standalone trigger, and its signals still fail regularly. ### How is the Accelerator Oscillator calculated? AC equals the Awesome Oscillator minus a 5-period simple moving average of it; the Awesome Oscillator is the 5-period SMA of median price (high plus low, halved) minus the 34-period SMA of the same input. Every component is a simple average, which is why the result is smooth but lagged. ### What do the green and red bars on the Accelerator Oscillator mean? Color encodes change, not sign: a column is green when higher than the previous column and red when lower, whichever side of zero it occupies. A red column above zero means upside acceleration is fading; a green column below zero means downside acceleration is easing. ### Does the Accelerator Oscillator really lead price? Only in a restricted sense. It is computed entirely from past prices, so it contains no information price lacks; it differences the data twice, and differences of a smoothed series often turn before the series itself. The earlier turn costs more false ones, which is what the consecutive-column rules filter. ### Is divergence on the Accelerator Oscillator reliable? It marks genuine deceleration, but deceleration precedes pauses as well as reversals, so an AC divergence alone is thin evidence. Most practitioners require structural confirmation, a broken swing or failed retest, before trading one, whether regular or [hidden](https://www.luxalgo.com/library/concept/hidden-divergence/). Divergences against strongly trending markets fail most often. ## Implementations in the Library - Accelerator Oscillator (LuxAlgo, the standard build of the classic formula): https://www.luxalgo.com/library/indicator/accelerator-oscillator/ ## Related concepts - Balance of Power: https://www.luxalgo.com/library/concept/balance-of-power/ - CCI: https://www.luxalgo.com/library/concept/cci/ - Williams %R: https://www.luxalgo.com/library/concept/williams-percent-r/ - Ultimate Oscillator: https://www.luxalgo.com/library/concept/ultimate-oscillator/ - True Strength Index: https://www.luxalgo.com/library/concept/true-strength-index/ - Relative Vigor Index: https://www.luxalgo.com/library/concept/relative-vigor-index/ - Awesome Oscillator: https://www.luxalgo.com/library/concept/awesome-oscillator/ - Gator Oscillator: https://www.luxalgo.com/library/concept/gator-oscillator/ - Elder Ray: https://www.luxalgo.com/library/concept/elder-ray/ - Elder Impulse System: https://www.luxalgo.com/library/concept/elder-impulse-system/ --- Source: https://www.luxalgo.com/library/concept/accelerator-oscillator/ (LuxAlgo Library, the encyclopedia of trading & technical analysis). Free to use with attribution: https://www.luxalgo.com/library/license/