ATR calculator
Average true range from your bars, and ATR stops.
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Mass index calculator
Whether the bars' ranges are bulging, and the classic sign that a move may be about to turn.
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The bars
The mass index
The mass index is 25.94. No reversal bulge: it has not risen above 27 in the 40 bars it covers.
- The ranges
- It is falling, from 25.98 on the bar before. Above 25, the bars' high-to-low ranges have been widening against their recent average; below 25, narrowing.
- How it is read
- Dorsey's signal is the reversal bulge: the index climbs above 27 and then drops back below 26.5. Many traders read it as a sign that the current move may turn, and take the direction from another tool.
- Read it with care
- It measures the range only, not direction, so a bulge says a turn is more likely, not which way. Bulges are rare and do not always lead to a turn.
The bar's range and the mass index on the last bars (9-bar averages, 25-bar sum). The last bar is marked.
| Bar | Range | Mass index |
|---|---|---|
| 7 ago | 23.40 | 26.07 |
| 6 ago | 33.40 | 26.05 |
| 5 ago | 29.10 | 26.09 |
| 4 ago | 19.10 | 26.00 |
| 3 ago | 40.20 | 26.07 |
| 2 ago | 26.10 | 26.08 |
| 1 ago | 13.40 | 25.98 |
| Last | 25.10 | 25.94 |
Education only, not investment advice. The answer comes from the numbers you typed in, not from your account or the market. Simulated results are hypothetical and have limits: real trading has slippage, gaps, changing results and emotions. Trading leveraged products can lose money quickly, including all of it. Risk warning
Educational only, not financial advice; trading involves risk.
Turns start with wider bars
Donald Dorsey introduced the mass index in 1992. It takes each bar's range from high to low, smooths it with a 9-bar exponential average, divides that by a second 9-bar average of the first, and adds up the last 25 ratios. When the ranges widen quickly the sum swells: the bulge Dorsey watched as a warning that the trend may reverse.
Measure the size of the ranges with the ATR calculator, check whether the market is ranging with the choppiness index, and size the trade with the position size calculator.
Not advice. Arithmetic on the bars you type; an indicator describes the past bars, not the next one.
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Baroq never holds your money and never trades for you. Educational only, not financial advice; trading involves risk.