Opening range breakout as rules: a testable ORB card for MES

The opening range breakout written as explicit rules for index futures: range, trigger, entry, stop, 2R target, time exit and the days to stand aside.

The opening range breakout (ORB) is one of the oldest intraday ideas: let the market print its first range of the day, then act only if price leaves that range. It is simple to describe and easy to trade badly, mostly because of vague rules: a range that changes with mood, late entries, and stops moved because the trade "should" work.

This guide writes the ORB as an explicit rule set for an index future such as the Micro E-mini S&P 500 (MES). It is not a claim that the setup makes money. Treat it as a hypothesis: write the rules down, test them on past charts and in simulation, journal every occurrence, and keep, fix or drop the setup based on your own numbers.

Why the open, and which open

Equity index futures trade almost around the clock. CME Group lists the CME Globex hours for its equity index futures, including MES, as Sunday 6:00 p.m. to Friday 5:00 p.m. Eastern time, with a daily maintenance break from 5:00 p.m. to 6:00 p.m. ET. Check the current schedule on the CME Group MES contract specifications page before relying on it, because hours and holiday schedules change.

So the "open" here is not the futures session start. It is the 9:30 a.m. ET (8:30 a.m. CT) opening of the US cash stock market, when the index stocks begin trading and participation usually jumps. That surge creates a meaningful first range, and also makes the first minutes erratic.

For reference, CME Group lists MES at $5 times the S&P 500 Index, with a minimum tick of 0.25 index points worth $1.25. One full point is therefore $5 per contract. Every dollar figure below uses those values.

The rules, step by step

1. Define the range

Pick one window and never change it mid-test: either the first 15 minutes (9:30 to 9:45 a.m. ET) or the first 30 minutes (9:30 to 10:00 a.m. ET). The opening range high is the highest traded price in that window; the low is the lowest. Use the futures contract you will actually trade, not the cash index.

The 15-minute version triggers earlier with tighter stops but more opening noise; the 30-minute version is wider and trades less often. Test one at a time.

2. Check the cancel conditions before anything else

The setup is cancelled for the day if any of these is true:

• Scheduled release inside the trade window. If a major report (CPI, the jobs report, an FOMC decision or Fed chair press conference) lands between the range start and your time exit, stand aside. Check the BLS release schedule and the Federal Reserve FOMC calendar during your pre-market plan.
• Large gap. If the price at 9:30 is outside the prior day's regular-session high-to-low range, skip. Gap days behave differently and deserve their own rules.
• Range too wide. If the opening range is more than 1.5 times the average of the last 10 opening ranges (measured the same way), skip. A wide range means a wide stop and a small position, and much of the day's move may already be used up.
• Range too narrow. If it is less than half that 10-day average, skip. A tiny range is easily broken by noise, so it produces a lot of false triggers.
• You are already at your daily loss limit, or this would be a third ORB attempt today.

The 1.5x and 0.5x thresholds are illustrative starting points, not tested values. The point is a number written down before the open.

3. Trigger

A long trigger is a completed 5-minute bar that closes above the opening range high. A short trigger is a completed 5-minute bar that closes below the opening range low. Requiring a bar close, not a single tick through the level, filters some quick pokes that reverse at once, at the cost of a worse entry on days that run.

4. Entry

After a long trigger, place a buy stop order one tick above the high of the trigger bar (mirror this for shorts). If it is not filled within the next two 5-minute bars, cancel it. If price closes back inside the range before you are filled, cancel it. Only one entry per direction per day.

5. Stop placement: pick one option and keep it

• Opposite side of the range. The cleanest invalidation: if price crosses the whole range, the breakout idea is clearly wrong. It is also the widest stop.
• Range midpoint. Half the distance, so double the contracts for the same dollar risk, but more trades stopped by ordinary back-and-forth.
• Trigger-bar low (for longs) or high (for shorts). Tightest, most often hit. Only test this once the other two are measured.

Whichever you pick, the distance from entry to stop is 1R, and the position size comes from it. See the risk topic for sizing from a fixed dollar risk.

6. Target in R

Exit the whole position at 2R (twice the entry-to-stop distance). One fixed target keeps the test honest; scaling out or trailing can be tested later as separate versions.

7. Time-based exit

No new entries after 11:00 a.m. ET. Any open position is closed at market at 11:30 a.m. ET. Breakouts that have not worked by late morning often drift into the quiet midday, and an open-ended trade is not a rule.

The rule card

ORB rule card, version 1 (fill in your own values before testing)

Item	Rule
Instrument	MES, front month ($5 per point, 0.25-point tick = $1.25)
Range window	9:30 to 10:00 a.m. ET (30 minutes)
Cancel if	Release in window; open outside prior-day range; range over 1.5x or under 0.5x its 10-day average; daily loss limit hit
Trigger	5-minute close beyond the range high or low
Entry	Stop order 1 tick beyond trigger bar; cancel after 2 bars or a close back inside
Stop	Range midpoint
Risk per trade	Fixed dollar amount; contracts = risk budget / (stop distance in points x $5), rounded down
Target	2R, full exit
Time exit	No entries after 11:00 a.m. ET; flat by 11:30 a.m. ET
Max attempts	One per direction, two per day

Worked example

Illustrative example: the numbers below are round figures chosen to show the arithmetic. They are not a real trade or a forecast.

From 9:30 to 10:00 a.m. ET, MES trades between 4,990.00 and 5,010.00, a 20-point range. The 10-day average range is 18 points, so 20 is inside the 9-to-27 band. There is no release before 11:30 and the open was inside the prior day's range. The setup is live.

At 10:15 a 5-minute bar closes at 5,012.00 with a high of 5,013.00. The buy stop goes at 5,013.25 and fills on the next bar. The stop is the range midpoint, 5,000.00.

Illustrative ORB long in MES

Line	Calculation	Result
Stop distance (1R)	5,013.25 - 5,000.00	13.25 points
1R per contract	13.25 x $5	$66.25
Risk budget	Illustrative	$150
Contracts	$150 / $66.25 = 2.26, rounded down	2
Target (2R)	5,013.25 + 26.50	5,039.75
Gross at target	26.50 x $5 x 2	+$265.00
Gross at stop	-13.25 x $5 x 2	-$132.50
Costs	Illustrative $2 per contract round turn in commissions and fees, plus 1 tick slippage on the stop exit	About $4 to $6.50

If neither level is reached by 11:30, the position is closed at market and recorded as whatever R it was worth, for example +0.4R or -0.6R. Check your own commission and exchange fee schedule; the cost line here is a placeholder.

Notice what costs do to small targets. On a single MES contract, a $5 round-trip cost is about 0.08R here. With a 4-point stop it would be about 0.25R, which is why very narrow ranges get cancelled.

What goes wrong

• False breakouts. Price closes beyond the range, you are filled, and it reverses straight back through the level to your stop. This is the normal failure mode, not a rare one. If your journal shows it dominating, test the 30-minute window or the far-side stop rather than adding indicators.
• Chasing. Entering late, far from the trigger, enlarges the stop distance without changing the target, so the real reward-to-risk is worse than the card says. If the order did not fill under the rules, the trade did not exist.
• Slippage. Stop orders fill at the next available price. In fast moves at the open or on surprise headlines, entries and stop-outs can be several ticks worse than planned. Record planned versus actual fill on every trade.
• Two-sided days. Both directions trigger and lose; hence the two-attempt cap.
• Rule drift and doubled exposure. Changing the stop or target after a few losers creates a new version; start a fresh count. Running the ORB in MES and the Micro E-mini Nasdaq-100 together is often one bet twice, so count it against one risk budget.

How to test and journal it

1. Write version 1 of the card before looking at any charts.
2. Replay at least 40 past sessions in order and mark each day: cancelled (and why), no trigger, or trade.
3. For each trade, log range size, direction, planned and actual entry, stop, exit reason (target, stop or time) and result in R after costs.
4. Run the same card in simulation for a few weeks with the same log.
5. Review trade count, win rate, average win and loss in R, and time exits. Keep, fix or drop; if you fix, change one rule only.

The process topic covers journaling and weekly reviews in more detail, and the futures topic covers contract mechanics. For the day's scheduled events, start with the market news page.

Examples use round, illustrative numbers and are not actual trades or results. Education only — not investment, tax or legal advice.

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