Cutoff CO Opening Range Guide: From Theory to Practice

Positional Scenario Explanation

The Cutoff (CO) is the position after the under-the-gun positions and before the Button. The CO is the third-best seat at the table, right behind the button and the small blind? Actually, the positional advantage ranking is: BTN > CO > HJ > MP... But the CO has a positional advantage and usually faces fewer players acting. On a full 9-handed table, the CO sits after the LJ (left-jack) and directly faces the button and the blinds. The CO’s opening range is relatively wide because you have the opportunity to retain positional advantage in later streets (unless the button calls or re-raises).

Recommended Range (Text Description)

Typical CO opening range (effective stacks 100BB, no ante):

• Value hands: All pairs (22-AA), all suited aces (A2s-AKs), offsuit big aces (ATo-AKo), KQo, KJs+, QJs+, JTs, T9s.
• Mixed hands: Some offsuit medium-low connectors (e.g., JTo, T9o, 98o) and suited gapped connectors (e.g., J9s, T8s, 97s) can be selectively added.
• Overall frequency: About 22%–25% of hands, roughly 290–330 combinations.

More detailed breakdown:

• Strong opens: TT+, ATs+, KQs+, AQo+ – these hands usually continue against a 3-bet.
• Medium strength: 22–99, A9s–A2s, KJs–KTs, QJs, JTs, T9s, 98s, 87s (suited connectors), ATo, KQo.
• Exploitative hands: When opponents defend too little, you can add A8o–A2o, KJo, QTo, JTo, T9o, etc.

Range Construction Logic

The CO opening range follows a value-[bluff] balance principle:

1. Value portion: Strong made hands (pairs and big card combos) to extract value and protect your range.
2. Bluff portion: Suited connectors, suited aces, and other hands with development potential to balance the value hands and maintain aggression.
3. Positional advantage: The CO usually has position postflop, so you can widen the range and use flop aggression to attack the blinds’ weak ranges.
4. Blind defense: The blinds will fight back, but their ranges are weaker, so the CO should put constant pressure on the blinds but also avoid being isolated by the button.

Adjustment Factors

• Blind style: If the blinds 3-bet frequently or call loosely, tighten up (drop bottom marginal hands); if they fold too much, widen your range.
• Button style: If the button is aggressive, the CO should reduce marginal hands to avoid being squeezed; if the button is tight-passive, you can steal more often.
• Stack depth: Short-stacked (<30BB) – tighten up, reduce suited connectors; deep-stacked (>150BB) – you can add more speculative hands like suited connectors.
• Ante structure: With an ante, pot odds are better, so widen your range; without an ante, tighten slightly.
• Number of players: Short-handed (6-max) is wider than full ring because the rotation is faster.

GTO Reference

Under the GTO framework, the CO opens about 25% of hands. The exact range depends on the solver, but typical features:

• All pairs are opened (22+)
• All suited aces (A2s+)
• Offsuit aces: ATo+, AJs+, AQo+, AKo (all A-high)? Actually in GTO A2o is a fold, but ATo+ is opened fully.
• KQo, KJs+, KTs+ (but KTo folds)
• QJs, QTs (QTo folds)
• JTs, J9s (JTo is marginal)
• T9s, T8s (T9o folds)
• 98s, 87s, 76s, 65s etc. – suited connectors, but with decreasing frequency.

Note: GTO ranges differ from exploitative ranges and should not be blindly applied.

Practical Application

1. Against tight-passive blinds: Steal with about 30% of hands, especially marginal hands like A2o, KJo.
2. Against aggressive 3-bettors: Tighten to about 20% to avoid being exploited; at the same time, increase your 4-bet range and fight back with hands like KQs, ATs.
3. Calling 3-bets: Your defense range against a 3-bet should include: all pairs (22–77 flat, 88+/AQ+ sometimes 4-bet), suited connectors (T9s+), A8s+, K9s+, etc. But adjust according to 3-bet sizing.
4. Postflop strategy: The CO has position postflop, so the c-bet frequency is higher. Against the blinds’ ranges, you can use about 70% continuation bets with a 2/3 pot sizing. However, consider board texture.
5. Example: Effective stacks 100BB, CO opens 2.5BB with 87s, button folds, both blinds call. Flop Q♠9♣4♦. You have a backdoor straight and flush draw – you can make a small c-bet semi-bluff.

Summary

The cutoff opening range is one of the cores of profitability, requiring constant adjustment based on opponents and dynamics. Remember: the wider the range, the higher the demand for post-flop skills. First master the basic range (22%), then gradually add exploitative adjustments.