Cutoff CO Opening Range Guide: From Basics to GTO Strategy

Position Summary

The Cutoff (CO) is located to the right of the Button (BTN), one seat before the dealer. Due to having position advantage post-flop (second only to the BTN) and being able to directly observe actions from earlier positions, the CO is one of the most profitable positions in Texas Hold'em. Compared to earlier positions, the CO can enter pots wider while maintaining leverage over later players (BTN, blinds).

In a standard 6-max game, the CO faces three main scenarios when opening:

• All players before the CO fold, action is on the CO (most favorable)
• A player before the CO limps, requiring the CO to decide whether to raise or call (typically raise)
• A player before the CO raises, requiring the CO to decide whether to 3-bet, call, or fold (here we only discuss CO opening, i.e., when no one has raised before)

Recommended Range (Hand Types Described Textually)

Below is the suggested CO opening raise hand range for a standard 6-max game with 100BB effective stacks (when no one has raised before):

• Value Raises: All pairs (22+), all suited aces (A2s+), A9o+, KQo, KJs+, QJs, JTs, T9s, 98s, 87s, 76s, 65s.
• Mixed Raise/Call (against aggressive blinds): ATo, KJo, QTo, JTo, T9o, 98o, 87o (these hands can be considered for direct raise if blinds are aggressive; if blinds are passive, they can be folded more often).
• Top of Range: TT+, AQo+, AJs+, KQs (these are very strong from CO, usually raised and not folded to a 3-bet).
• Bottom of Range: 65s, 76s, 87s, K9s, Q9s, J9s, T8s, 97s, 86s, 75s (suited connectors and suited gappers used to balance range and leverage position).

Note: The above range is a basic version; actual range should adjust based on opponents. Generally, the CO opening raise range is about 20-25% of hands, approximately 260-330 combinations (out of 1326).

Range Construction Logic

The CO range construction is based on the following core principles:

1. Position Advantage Premium: Due to being relatively late post-flop, you can enter pots wider. Compared to UTG (about 15-17%), the CO range can increase to 20-25%.
2. Avoid Limping: In modern GTO strategy, the CO almost always raises to enter the pot; limping exposes range weaknesses and lets the blinds see free flops. Unless in specific situations, limping is not recommended.
3. Suited Connectors and Small/Medium Pairs: These hands have playability in multiway pots but are vulnerable to squeezes. The CO is an ideal position to introduce these hands because only the BTN and blinds can potentially squeeze.
4. Blocker Effect: For example, holding A2s blocks AA and also has value on A-high flops. The CO range should include enough small aces (e.g., A2s-A5s) to balance post-flop betting ranges.
5. Balance vs. Exploitation: The basic range focuses on balance, but if blinds fold too often, you can significantly widen the range; conversely, tighten if needed.

Adjustment Factors

In actual gameplay, the CO range needs dynamic adjustments based on:

• Opponent Tendencies:
  • Blind Players: If blinds frequently 3-bet, tighten the range, reducing low-quality suited connectors and weak aces; if blinds fold often, add more marginal hands (e.g., K9o, QTo).
  • BTN Player: If the BTN is passive (rarely 3-bets), widen the range; if the BTN is aggressive, consider their squeeze and keep some strong hands for defense.
• Stack Depth:
  • Shallow Stacks (<40BB): Focus more on strong hands, reduce suited connectors, and increase high cards (e.g., KJo, ATo) to simplify decisions.
  • Deep Stacks (>150BB): Can widen the range, use more suited connectors and small/medium pairs, leveraging implied odds post-flop.
• Limpers from Early Position: When there are limpers ahead, typically isolate with a raise of about 3-4BB + 1BB per limper. The range should be slightly wider than a pure open (due to better pot odds), but be aware of potential trap setups by limpers.
• Tournament ICM Pressure: Near the final table or money bubble, the CO range needs significant tightening to avoid conflicts with short stacks.

GTO Reference

From a GTO (Game Theory Optimal) perspective, the CO opening range should maintain balance to avoid exploitation. Below is a simplified GTO range reference (6-max, 100BB):

• Raise range: Approximately 23% of hands, including:
  • Value hands: [JJ]+ , AK, AQ, [AJs], [KQs] (about 5%)
  • Mixed hands: [TT]-[77], [ATs]-[A9s], [AJo]-ATo, [KQo], [KJs], [QJs], [JTs], [T9s], [98s], 87s, 76s, 65s (about 18%)
• Fold range: The remaining 77% of hands.
• Raise size: Standard 2.5-3 BB; when there are limpers, [raise] to 3-4 BB + 1 BB per limper.

Note: In GTO, the CO range is not fixed—it adjusts based on the 3-bet frequency of subsequent players. If the BTN or blinds have an overly narrow 3-bet range, the CO can significantly widen its range and raise frequently; if the 3-bet range is too wide, tighten up and increase [4-bet] frequency.

Practical Application

Example 1: Standard 6-max, effective stack 100 BB, all players fold to CO

• Holding A2s: Raise to 2.5 BB. Flop comes A73 rainbow, c-bet 2/3 pot. If raised, call or fold based on opponent's tendencies.
• Holding KJo: Raise to 2.5 BB. Flop comes K62 rainbow, bet half pot. If the BTN or a blind raises, evaluate their range and possibly fold (since KJo is difficult to improve against top pair or middle pair).

Example 2: The blinds are very tight players (VPIP < 15, 3-bet < 3%)

• Significantly widen your range: You can raise hands like [T8o], [97s], [K9o], etc. Even if you miss the flop, tight blinds often have weak hands with high fold equity.
• Note: If the BTN is aggressive, beware of squeeze plays and selectively fold some marginal hands.

Example 3: The blinds are aggressive 3-bettors (3-bet > 12%)

• Tighten your range: Fold all weak suited connectors (e.g., 65s, 87s) and weak Ax (e.g., A2s-[A5s]), keeping only JJ+, AQ+, KQo, AJs+, KJs, QJs, JTs, T9s, etc.
• [4-bet range]: Use [QQ]+, AK, [AQs] for value [4-bets]; use A5s, [A4s], etc., as bluff [4-bets] (because they block AA, KK, AK).

The CO open is the foundation of profitability. Mastering range construction and adjustment allows you to build a huge advantage preflop. Remember: Position is the core of cash games; the CO is the golden seat just behind the BTN. Use your range width and balance wisely.