Mass Index Indicator Explained

Donald Dorsey's Mass Index ignores direction entirely: it sums a ratio of smoothed range EMAs over 25 bars, and watches for a 'bulge' — the range swelling and then contracting. The bulge pattern historically precedes trend reversals, whichever way the trend was pointing.

How It Works

• EMA(high−low) ÷ EMA(EMA(high−low)), summed over 25 bars.
• The classic bulge: index rises above 27, then falls back below 26.5.
• No directional information — pure reversal timing.

How to Trade It

When the bulge completes, take direction from something else — a 9-period EMA slope, structure break, or Supertrend flip — and trade the reversal it points to. As a filter, an in-progress bulge is a reason to tighten stops on trend positions.

Building It in Setup.Cash

Add Mass Index in the strategy builder — the length input controls its sensitivity — and use its value in any entry, exit, or filter condition. You can also combine it with other tools in the Indicators Lab or via the AI indicator generator. See the Swing High/Low Detector for the structural confirmation half. For the full category overview, see the volatility & statistics library guide.

Volatility indicators qualify trades rather than generate them — backtest your system with and without this filter and compare the drawdowns.