McClellan Oscillator
The McClellan Oscillator is a market breadth indicator: the 19-day EMA of net advances (advancing minus declining stocks) minus the 39-day EMA. Above zero suggests broad buying, below zero broad selling; its running total is the McClellan Summation Index.
An index can rise while most of its stocks fall, if a few giants carry it. Breadth indicators check whether the crowd is joining in. The McClellan Oscillator turns the daily count of rising and falling stocks into a MACD-style momentum line. This entry explains the formula, the ratio-adjusted version, signals and the Summation Index.
- Category
- Indicators and Tools
- Reading time
- 3 min
- Also called
- McClellan breadth oscillator, McClellan Summation Index
- Updated
The McClellan Oscillator in plain words
Developed by Sherman and Marian McClellan, it is a breadth indicator built from net advances: advancing issues minus declining issues.1
It equals the 19-day EMA of net advances minus the 39-day EMA, which makes it work much like MACD.1
Adding up the daily oscillator values gives the McClellan Summation Index.2
How the oscillator is calculated, step by step
Count advances and declines
On an exchange such as the NYSE.
Net advances
Advances − declines.
Ratio-adjust (optional)
(Advances − declines) ÷ (advances + declines).
19-day EMA
Short-term breadth trend. See Moving Average.
39-day EMA
Longer-term breadth trend.
Subtract
19-day EMA − 39-day EMA = oscillator.
Worked examples
Example 1 — Ratio-adjusted net advances
Broad advance2,000 stocks advance and 1,000 decline.
| Net advances | 2,000 − 1,000 = 1,000 |
| RANA | 1,000 ÷ 3,000 ≈ 0.333 |
Ratio adjustment expresses net advances as a share of advances plus declines.1
Example 2 — The oscillator value
+15019-day EMA of net advances is +250; the 39-day EMA is +100.
| Oscillator | +250 − (+100) = +150 |
A positive reading means short-term breadth is stronger than the longer trend.1
Example 3 — Summation Index
+740Yesterday's Summation Index was +800; today's oscillator is −60.
| New Summation Index | +800 + (−60) = +740 |
The Summation Index is the previous value plus the current oscillator reading.2
McClellan Oscillator vs Summation Index
| Aspect | Oscillator | Summation Index |
|---|---|---|
| Calculation | 19 EMA − 39 EMA of breadth | Running total of the oscillator |
| Speed | Fast | Slower |
| Best for | Short-term momentum | Medium-term trend |
| Signals | Thrusts, zero crosses, divergences | Direction, crosses, divergences |
How traders use the McClellan Oscillator
Breadth thrusts
Sharp jumps show broad buying.
Zero-line crosses
Shifts in breadth momentum.
Divergences
Index highs without breadth confirmation. See Divergence.
Market timing
Context for index trades. See Market Breadth.
Advantages and disadvantages
Advantages
- Shows participation behind index moves.
- Familiar MACD-style reading.
- Ratio-adjusted version is comparable over time.
Disadvantages
- Only for broad markets, not single stocks.
- Needs exchange breadth data.
- Signals can whipsaw.
Going deeper
Read as far as you need. Each level builds on the one before it.
Why ratio-adjust
Beginner
The number of listed stocks changes over time, so StockCharts ratio-adjusts net advances to keep readings comparable across years.1
Signals
Intermediate
Summation as an oscillator
Advanced
Despite its name, the Summation Index fluctuates above and below zero and can give its own divergence and crossover signals.2
Common mistakes
Using it on one stock
It needs many stocks' data.
Mixing adjusted and unadjusted values
Levels differ greatly.
Trading every zero cross
Look for strong moves or divergences.
Ignoring the index itself
Breadth confirms, it doesn't replace price.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- The McClellan Oscillator measures breadth momentum.
- Formula: 19-day EMA − 39-day EMA of net advances.
- Above zero means broad strength.
- Its running total is the Summation Index.
- Ratio adjustment makes readings comparable over time.
Frequently asked questions
What is a strong McClellan reading?
Which exchanges are used?
Is it a leading indicator?
Further learning
- Market Breadth
The wider family of breadth tools.
- MACD
The same structure applied to price.
- Arms Index (TRIN)
Another breadth measure.
- Divergence
A key McClellan signal.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- StockCharts ChartSchool. McClellan Oscillator (opens in a new tab) Checked .
- StockCharts ChartSchool. McClellan Summation Index (opens in a new tab) Checked .
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. We are not affiliated with any publisher linked above. Last reviewed . Report an error or request a source credit.