What Is the McClellan Oscillator? How to Use It in Trading

The McClellan oscillator can help traders look beneath the surface of an index move, showing whether participation across the wider market is expanding, narrowing or beginning to diverge from price.

Understanding the McClellan oscillator

The McClellan oscillator is a market breadth indicator that measures the momentum of advancing and declining stocks across an entire exchange. Developed by Sherman and Marian McClellan in 1969, it uses two exponential moving averages of daily net advances – the number of advancing issues minus the number of declining issues – and subtracts the slower EMA from the faster one. The result is a line that oscillates above and below zero, showing whether broad market participation is accelerating or decelerating.

Unlike price-based oscillators such as RSI or MACD, the McClellan oscillator does not derive its readings from an individual instrument’s price history. It measures the internal condition of an entire exchange, showing how many listed stocks are participating in a move, rather than only how far the headline index has moved. A major index can rise on the strength of a small number of large-cap constituents while most stocks decline; conversely, an index may fall while a growing number of individual stocks begin to stabilise. The McClellan oscillator can help identify these divergences in participation.

The McClellan oscillator reflects the breadth of a market move, not its magnitude. A rising index accompanied by a falling oscillator may suggest that fewer stocks are supporting the advance. Conversely, a falling index accompanied by a rising oscillator may suggest that selling pressure is becoming less broadly based. These are signals to monitor, not guarantees of reversal. Past performance is not a reliable indicator of future results.

How is the McClellan oscillator calculated?

The McClellan oscillator calculation starts with market breadth data, then smooths that data to show how participation is changing over time.

The formula

The McClellan oscillator starts with the daily net advances figure for the exchange being analysed:

Two exponential moving averages are then applied to this series, using smoothing multipliers that correspond to approximately 19 and 39 periods:

The multipliers come from the standard EMA formula. A 19-period EMA uses a multiplier of 2 ÷ (19 + 1) = 0.10, often called the ‘10% EMA’. A 39-period EMA uses a multiplier of 2 ÷ (39 + 1) = 0.05, known as the ‘5% EMA’. Each EMA is updated daily using the iterative formula:

Past performance is not a reliable indicator of future results.

Worked example

Assume the following inputs on a given trading day for a major exchange:

If the previous day’s 19-period EMA stood at +350 and the 39-period EMA stood at +200:

The positive reading shows that the faster EMA of net advances is running ahead of the slower EMA. In this example, breadth momentum is expanding in the advancing direction. Conversely, if declining issues outnumbered advancing issues and the faster EMA moved below the slower EMA, the oscillator would produce a negative reading, suggesting that breadth momentum was moving in the declining direction.

Using the McClellan oscillator on a price chart

The McClellan oscillator is usually plotted as a line beneath the exchange index it monitors, most commonly the NYSE Composite or Nasdaq Composite. A horizontal zero line divides the indicator panel, while reference lines at +100 and −100 mark the conventional overbought and oversold thresholds. Most platforms that carry the oscillator display it alongside the index, helping traders compare the headline price level with the breadth conditions behind it.

Past performance is not a reliable indicator of future results.

How the McClellan oscillator works in trading

Traders typically interpret the McClellan oscillator by looking at where it sits, how far it has moved, and whether it confirms or diverges from the index price.

Zero line crossings

When the oscillator crosses above zero, the faster EMA of net advances has moved above the slower EMA, meaning the pace of breadth improvement is accelerating. Conversely, when it crosses below zero, breadth deterioration is accelerating. Traders generally use these crossings as signals about broad market momentum, rather than direct entry triggers for individual instruments.

A bullish zero line cross is usually more meaningful when it follows sustained negative breadth readings and the oscillator had been clearly oversold before turning. Conversely, a bearish zero line cross may carry more analytical weight when it follows a prolonged overbought phase, or when the index has advanced without broad participation behind it.

Overbought and oversold readings

Readings above +100 indicate that breadth momentum is expanding strongly, with the 10% EMA of net advances running well ahead of the 5% EMA. Conversely, readings below −100 indicate broad-based and accelerating selling pressure. Both extremes show that breadth momentum has stretched significantly from neutral, rather than offering precise reversal signals.

In a strongly trending market, the oscillator can remain above +100 for extended periods without the trend reversing. The more useful signals at these extremes often come from the turn back toward the zero line. When the oscillator peaks above +100 and begins to move lower, the pace of breadth expansion may be slowing. Conversely, when it troughs below −100 and begins to recover, selling pressure may be losing breadth.

Breadth thrust

A breadth thrust is a rapid recovery from deeply oversold readings below −100, back through zero and into overbought territory above +100, usually within around 10 trading days. This sharp reversal in participation, from broad-based selling to broad-based buying, is treated by some breadth analysts as one of the more notable conditions the oscillator can identify. Conversely, a sharp move from above +100 to below −100 may point to a rapid deterioration in participation. Neither condition appears frequently, and neither guarantees subsequent price movement. Past performance is not a reliable indicator of future results.

Best McClellan oscillator settings for different trading styles

The standard McClellan oscillator settings suit many daily-chart applications, but some traders adjust the inputs depending on their timeframe and analytical objective.

Standard 19/39 settings (10% and 5% EMAs)

The standard settings, as defined by Sherman and Marian McClellan, use 19 and 39 periods, corresponding to smoothing multipliers of 10% and 5%. These are the default settings on most platforms that carry the indicator and are designed to capture intermediate-term breadth cycles over weeks to months. They are most relevant to traders using daily charts who want a broad view of whether market participation is expanding or contracting.

Modified settings for shorter cycles

Some traders reduce the EMA periods to capture faster breadth cycles. A common variant uses 10 and 20 periods, which correspond to approximately 18% and 9% smoothing. This creates a more reactive oscillator that reflects near-term breadth shifts more quickly and may suit traders focused on shorter-term setups.

The trade-off is a higher frequency of zero line crossings and extreme readings, which increases both the number of signals and the risk of false positives. Shorter settings also amplify day-to-day noise in the advance-decline data.

Adjusted Net Advances version

The original formula uses raw net advances. A modified version, the McClellan oscillator with Adjusted Net Advances, normalises net advances by total issues traded before applying the EMAs:

This percentage-based approach accounts for changes in the number of issues listed on an exchange over time, making readings more comparable across longer historical periods. Many modern charting platforms offer this option alongside the raw version. No single setting is optimal for all market conditions. Testing the indicator on a demo account can help traders understand how it behaves before applying it to live analysis.

Core McClellan oscillator trading strategies

The following strategies show how traders may use the McClellan oscillator as part of a broader technical analysis process, rather than as a standalone trading signal.

Past performance is not a reliable indicator of future results.

Past performance is not a reliable indicator of future results.

McClellan oscillator divergence strategy

Divergence can help traders assess whether index price moves are being confirmed by wider market participation.

Past performance is not a reliable indicator of future results.

Divergence doesn’t guarantee a reversal. In strong trends, the oscillator can diverge across several highs or lows before price changes direction. Use divergence as supporting context, not as a standalone trigger.

Combining the McClellan oscillator with other indicators

Because the McClellan oscillator focuses on breadth momentum, it can provide more context when used alongside indicators that measure trend, volume or longer-term participation.

Advance-decline line

The advance-decline line (A-D line) is a cumulative running total of daily net advances. While the McClellan oscillator measures the momentum of net advances – their rate of change – the A-D line shows the cumulative trend over time.

Using both provides a layered breadth picture. The A-D line shows whether the broad market is in a sustained advance or decline at a structural level, while the McClellan oscillator identifies the pace and direction of change within that trend. Divergence between the A-D line and the index price is a widely observed breadth signal in its own right, and the oscillator can help traders assess timing around it.

McClellan Summation Index

The McClellan Summation Index is the running cumulative sum of all daily McClellan oscillator readings. It is a slower-moving, longer-term representation of breadth conditions. While the McClellan oscillator oscillates frequently around zero over short cycles, the Summation Index reflects the broader trend in market breadth across months.

Readings above +1,000 indicate a sustained period of strongly positive breadth; conversely, readings below −1,000 indicate a sustained negative breadth environment. Using the Summation Index for trend context and the Oscillator for timing creates a multi-timeframe breadth framework that many breadth analysts use.

Arms Index (TRIN)

The Arms Index, also known as TRIN, measures the ratio of advancing to declining issues against the ratio of advancing to declining volume. It adds a volume dimension to the breadth picture that the McClellan oscillator does not provide on its own. When the oscillator signals improving breadth but TRIN remains elevated, indicating heavy volume concentrated on the declining side, the breadth improvement may be less reliable. Conversely, improving oscillator readings alongside falling TRIN can provide a more robust signal than either indicator alone.

Volume breadth indicators

Volume-based breadth tools such as the Upside/Downside Volume ratio pair naturally with the McClellan oscillator by showing whether participation in advancing issues is backed by volume. A rising McClellan oscillator supported by expanding upside volume provides a more complete picture of broad buying activity. Conversely, when the oscillator is improving but upside volume does not confirm the move, the breadth improvement may be driven by a large number of stocks making small gains rather than stronger directional moves.

No single indicator is definitive. Combining the McClellan oscillator with complementary breadth tools can improve context and reduce the risk of false positives.

Common mistakes and how to avoid them

Like any technical indicator, the McClellan oscillator can be misread when used without context. The following points cover common interpretation issues and how traders may reduce them.

Treating zero line crosses as direct entry signals

• The McClellan oscillator is an exchange-wide indicator.
• It reflects the behaviour of many listed issues, not one individual stock.
• A zero line cross doesn’t account for:
  • the stock’s own technical setup
  • sector trends
  • company-specific factors
• Use it to assess the broader market backdrop, not as a standalone entry trigger.

Acting on every overbought or oversold reading

• Overbought or oversold readings show an extreme in breadth momentum, not an immediate reversal.
• In strong trends:
  • readings above +100 can last for days or weeks
  • readings below -100 can persist during broad sell-offs
• Entering on the first touch of +100 or -100 can mean positioning too early against the trend.
• Traders may reduce this risk by waiting for a confirmed turn back towards the zero line.

Comparing raw readings across time periods

• Raw net advances are affected by the number of issues traded on an exchange.
• A reading of +200 in 1990 may not represent the same market breadth as +200 today.
• This is because the number of listed stocks changes over time.
• For analysis across multiple decades, the percentage-based ANA version may be more suitable.

Using the indicator on individual instruments

• The McClellan oscillator needs exchange-level advance-decline data.
• It is designed to measure broad market participation.
• Applying it to a single stock, currency pair or commodity removes its breadth-related meaning.
• Single instruments don’t have advancing and declining issues in the same way a market does.

Ignoring the Summation Index context

• A zero line crossover can mean different things depending on the McClellan Summation Index.
• A bullish crossover may be less meaningful if the Summation Index is deeply negative and falling.
• A bearish crossover may be a shorter-term pullback if the Summation Index remains positive and rising.
• Checking the Summation Index can help place oscillator signals in their wider breadth context.

Create an account Open a demo account

FAQ