Breakout Probability Expo Indicator: Three ATR Windows

Written by Dominic Walsh · Published 2 Jun 2026 · Last updated 21 Aug 2026

The breakout probability expo indicator measures how far price travelled over three windows. It reports each one in ATR units. Breakout N1, N2 and N3 carry the three readings. Threshold lines mark where a move counts as big enough to matter.

This build ships as a compiled .ex4 for MT4 and .ex5 for MT5; the screenshots below come from GBPUSD M15.

Platforms	MT4 (.ex4) + MT5 (.ex5)
Chart window	Separate window
Plots	8: Breakout N1, Breakout N2, Breakout N3, Zero, Upper Threshold, Lower Threshold, Breakout Buy, Breakout Sell
Alerts	popup
Inputs	7

What the Breakout Probability Expo Indicator draws on the chart

Breakout N1, Breakout N2 and Breakout N3 score the windows set by InpWindow1, InpWindow2 and InpWindow3.

Zero holds the flat centre line. These readings run both positive and negative.

Upper Threshold and Lower Threshold sit at plus and minus InpThreshold.

Breakout Buy and Breakout Sell mark the bars where scores clear a threshold.

• Breakout N1: histogram, lime, width 2
• Breakout N2: histogram, dodger blue, width 2
• Breakout N3: histogram, red, width 2
• Zero: line, silver, width 1
• Upper Threshold: line, gold, width 1
• Lower Threshold: line, gold, width 1
• Breakout Buy: arrow, lime, width 2, arrow code 233
• Breakout Sell: arrow, red, width 2, arrow code 234

How the Breakout Probability Expo Indicator calculates its values

Distance measured in ATR

Each window measures how far price moved across it. The ATR over InpAtrPeriod bars then divides that. What comes out is a distance in volatility units, not points.

When ATR reads zero the code uses a small floor instead. That keeps the pane working on thin data.

Why three windows

InpWindow1 at 10, InpWindow2 at 20 and InpWindow3 at 50 cover short, medium and long stretches.

A move scoring high on the short window alone is a spike. One scoring high on all three has lasted. Seeing all three at once is the point of the pane.

The exponential factor

InpExpoFactor weights the readings so a bigger move counts for more than its share. The scaling is not linear.

InpThreshold then sets where the lines sit, 2.0 by default. That means a move worth two ATR units over the window.

How to read the signals

All three lines above the upper threshold is the strongest reading this pane offers.

The short window clearing alone usually means a single fast bar rather than a move.

Everything works in ATR, so the same threshold means the same thing on any instrument.

The readings run positive and negative, so the zero line separates upward travel from downward.

Alert channels in this build: popup, one message per closed bar.

The one alert channel here is the MT4 popup. A bar time check runs first, so a threshold crossing raises one dialog per closed bar.

Every Breakout Probability Expo Indicator input

Core settings

Setting	What it does	Default
InpWindow1	Window N1 (short expo lookback). InpWindow1 is the shortest lookback, 10 bars by default.	10
InpWindow2	Window N2 (medium expo lookback). InpWindow2 is the middle window at 20.	20
InpWindow3	Window N3 (long expo lookback). InpWindow3 is the longest at 50.	50
InpAtrPeriod	ATR period for normalisation. InpAtrPeriod is the volatility window behind every score, 14 by default.	14
InpExpoFactor	Exponential expansion factor (>=1). InpExpoFactor weights larger moves more than proportionally, 1.25 by default.	1.25
InpThreshold	Signal threshold (in ATR units). InpThreshold sets where the two threshold lines sit, 2.0 by default.	2.0

Alert settings

Setting	What it does	Default
InpAlertOn	Alerts on/off. InpAlertOn gates the message block and defaults to true.	on

Settings that fit your chart

The screenshot uses GBPUSD M15. Working in ATR lets one threshold cover different instruments, so the defaults travel. M15 through H1 gives the three windows enough separation to disagree. On very slow charts the longest window reaches back a long way.

When the Breakout Probability Expo Indicator fails

The name says probability. The pane reports a scaled distance. Nothing here estimates a likelihood.

ATR expands after a fast move, so a genuinely large move can score lower than expected once volatility catches up.

Three windows over one price series often agree because they overlap. That is not independent confirmation.

InpExpoFactor is a convention, not a fitted value. The exact scores matter less than where they sit against the threshold.

Copy the compiled Breakout Probability Expo Indicator file into your MQL4/Indicators folder, and the MT5 build into MQL5/Indicators, then restart the terminal and drag it onto a chart. The step-by-step guide with screenshots is at how to install MT4 and MT5 indicators.

Hence, related on forexmt4systems.com: London Session Breakout Strategy.

Download the Breakout Probability Expo Indicator for MT4 and MT5

The zip holds the compiled Breakout Probability Expo Indicator build for MT4 and MT5, plus a short README. Compiled files only, no source. Enter your email below and the download link arrives in your inbox.

FAQ

Does this estimate an actual probability?

No, and the name overstates it. The pane reports how far price travelled over three windows, scaled by ATR and weighted by InpExpoFactor. That measures move size in volatility units. No likelihood appears anywhere in the source.

Why does InpAtrPeriod divide every score?

So one InpThreshold covers every instrument. A hundred point move means one thing on gold and another on a pair. Two ATR units means the same on both. Without it the threshold would need retuning per market.

What does it mean when only Breakout N1 clears the threshold?

The shortest window scored high while the other two did not. That usually means one fast bar rather than a real move. Seeing all three clear together is the reading worth acting on, which is why three windows appear rather than one.

What does InpExpoFactor 1.25 change?

It weights larger moves above their share, so a move twice as big scores more than twice as high. That spreads readings out near the extremes and squeezes them near zero. It is a presentation choice, not a measured property.

Are results guaranteed?

No. Trading involves risk. Results are not guaranteed; past performance is not indicative of future results. Use the Breakout Probability Expo Indicator as one input. Always backtest before trading live.