Mass Index¶
Indicators · Volatility
Mass Index — range-expansion reversal warning (Dorsey, 1992).
The Mass Index, created by Donald Dorsey, is a reversal-warning indicator that watches the range between highs and lows expand and contract. Its premise: trend reversals are often preceded by a widening of the daily range — the market "breathing in" before it turns. The Mass Index doesn't tell you which way price will reverse; it tells you a reversal is becoming likely, so you can pay attention and let a directional tool call the turn.
How it works¶
The block takes the high-low range, smooths it with an EMA, divides by a second EMA of that EMA, and sums the ratio over the Sum period (25) using the EMA period (9) for the smoothings. The signature signal is the "reversal bulge": the Mass Index rising above the Bulge threshold (27.0) and then falling back below the Trigger threshold (26.5). That bulge-then-drop is the warning — the Bulge signal fires when it completes. It plots as a line in a sub-pane with the two threshold guides.
When to use it¶
Use the Mass Index as a reversal alert, paired with a direction tool. When a bulge completes, a reversal of the current trend is statistically more likely — but since the Mass Index is directionless, you combine it with the prevailing trend (use a moving average) to know which way: a bulge in an uptrend warns of a top, in a downtrend a bottom. It's a "get ready" signal, not an entry; pair it with a structure break or oscillator turn for the actual trigger.
Example¶
Reversal warning in an uptrend: require a 50-EMA rising (uptrend) and the Mass Index Bulge signal (reversal becoming likely) — when both align, watch for a bearish Crosses Below trigger into a Sell Signal to fade the top. Backtest in the Tester.
Tips & gotchas¶
- Warns of reversal likelihood, not direction — pair with a trend tool for which way.
- The bulge-then-drop is the signal — rising above ~27 then falling below ~26.5.
- A "get ready," not an entry — combine with a directional trigger.
- Range-expansion based — it reads volatility breathing, not price level.
Related blocks¶
Inputs¶
| Socket | Type | What to wire in |
|---|---|---|
| Source | bars |
Price bars (needs high + low) |
Outputs¶
| Output | Type | Plots as | Description |
|---|---|---|---|
| MI | series |
Line · sub-pane | Mass Index value |
| Bulge | signal |
— | Reversal bulge: MI crossed above bulge threshold then back below trigger |
Parameters¶
| Parameter | Type | Default | What it does |
|---|---|---|---|
| EMA period | number · 2–100 | 9 |
|
| Sum period | number · 2–200 | 25 |
|
| Bulge threshold | number · 20.0–40.0 | 27.0 |
|
| Trigger threshold | number · 20.0–40.0 | 26.5 |
|
| Line color | colour | #ef5350 |
Chart guides
This indicator draws reference level(s): bulge_threshold, trigger_threshold.
Reference auto-generated from the block catalog · category Indicators.