Detailed Explanation of Cutoff CO Opening Range

Position and Scenario Overview

Cutoff (CO) is the second-to-last position to act in a six-handed table, located between the Under the Gun and Button positions. Since only the Button and blinds have yet to act, the CO has a positional advantage and can open wider than earlier positions, but must be wary of the Button's 3-bet squeeze.

Recommended Range

Generally, the CO opening range is about 20%-25% of total hands, specifically including:

• All pairs: 22+ (small pairs for stealing blinds or hitting sets)
• All Aces with kickers: A2s+, ATo+ (suited aces are good postflop, offsuit aces have decent kickers)
• All suited connectors: 45s+ (including suited one-gappers like 57s, 68s, etc.)
• Some high cards: KTo+, QJo+, K9s+, Q9s+, J9s+, T9s+ (all suited and offsuit hands with at least a Jack)
• Some suited ace-x: A2s-A5s (small suited aces for postflop flush draws and float plays)
• Excluded hands: Junk offsuit connectors (e.g., 32o), offsuit one-gappers (e.g., J8o)

Range Construction Logic

The CO range is built based on the following principles:

1. Positional value: The later the position, the more speculative hands (suited connectors, small pairs) can be added to take advantage of postflop positional advantage.
2. Blind stealing equity: When blinds fold often, the range can be wider; if blinds defend tightly, tighten up.
3. 3-bet defense: Against a Button 3-bet, need enough 4-bet bluffs and calling ranges. Typically the CO retains about 30-40% defense range (including 4-bets and calls).

Adjustment Factors

• Button style: If the Button 3-bets frequently, tighten the opening range (to about 18-20%) and increase 4-bet bluffs; if the Button is passive, widen to 25%+.
• Blind tendencies: If the small or big blind defends too wide (e.g., calling over 50%), reduce small pairs and low suited connectors, focus on high cards.
• Stack depth: Deep stacked (100BB+) can add more suited connectors; short stacked (≤40BB) should focus on strong hands (pairs, AJ+).
• Opponent tendencies: If blinds frequently 3-bet, reduce marginal hands and use A5s, A4s, etc. as 4-bet bluffs.

GTO Reference

According to common GTO solver results, at a six-handed table without antes, the optimal CO opening frequency is about 22%-24%. Against different opponents, refer to the following baselines:

• Button with no 3-bet tendency: open about 24%, moderate defense.
• Aggressive Button: reduce opening to 20%, and build about 8% 4-bet range (AA/KK/A5s, etc.).
• Loose fish in blinds: widen opening to 26%, but be cautious postflop.

Practical Application

Example 1: The blinds are tight-passive players, Button unknown. CO holds 76s, stack 100BB. Standard open (3BB). If Button folds, blinds are unlikely to call, often taking down the pot directly.

Example 2: Button is an aggressive reg. CO holds TT. Consider opening larger to 3.5BB to deter a 3-bet. If facing a 3-bet, decide between 4-betting or calling based on opponent's tendencies.

Example 3: Deep stacked (200BB) with wide blind calling ranges. CO holds AJo. Should be cautious opening, as postflop can be tricky. Recommend only raising strong hands.