Trends/Trend strength and direction

Mass index

Tracks widening and narrowing of the high-low range, without regard to direction.

Trend strength and directionBest on 1Y, 3YAlso called Dorsey mass index

Illustration of the mass index shape. It is a sketch, not real price data.

What it shows

Donald Dorsey's mass index smooths the high-low range with a 9-bar EMA and again with another 9-bar EMA. It divides the first by the second and adds up the last 25 values.

A reading above 27 followed by a drop below 26.5 is the 'reversal bulge' Dorsey described. We show the line and the two levels.

How we find it

The same code that draws it on your chart follows these steps, with the same result every time.

Range = high − low.
Single = EMA(9) of range. Double = EMA(9) of Single.
Ratio = Single ÷ Double.
Mass index = sum of the last 25 ratios.

Starting values: EMA 9; Sum 25; Levels 27 / 26.5. These are proposed and will be tuned on real price data before launch.

How to read it

The panel shows the mass index.
Dashed lines mark 27 and 26.5.
A bulge is a rise above 27 that falls back.

Status labels you may see

Label	What it means
Bulge	Rose above 27 and fell under 26.5 in the last 10 bars.
Above 27	Currently above 27.
Normal	Below 27, no bulge.

What cancels it

Ends when the index falls under 26.5.

What traders check next

Price trend at the time.
Moving average slope.
Range history.

Limits

Does not say direction.
Rare signals.
Not widely used.

Try it in forecastviz

Open any ticker and choose Trend strength and direction → Mass index in the left menu.
Switch between 1Y, 3Y to see how the picture changes.
Compare with Average true range and Bollinger bandwidth on the same chart.

Open on a ticker

Questions

What does it measure?

Whether ranges are widening.

Is a bulge a signal?

Dorsey said so. We make no claim.