Cutoff CO Opening Range Explained: A Complete Guide from Theory to Practice

Position Scenario Description

The cutoff (CO) is located to the right of the button (BTN) and is one of the last positions to act preflop. Due to its positional advantage, the CO can open-raise with a wider range while still retaining initiative over subsequent players (especially the BTN and the blinds). Understanding the CO's opening range is a key component of building an overall preflop strategy.

Recommended Range

The following is a typical CO opening raise range (for 100BB effective stacks, no limpers, standard 6-max):

• All pairs: 22+ (22 to AA)
• All AX suited: A2s+ (A2 suited to AK suited)
• All AX offsuit: ATo+ (AT offsuit to AK offsuit)
• All KX suited: K2s+ (K2 suited to KQs)
• KX offsuit: KJo+ (KJ offsuit to KQo)
• All suited connectors: 54s+ (54 suited to AKs, but note AKs is already in the AX range)
• Suited gappers: J9s, T8s, 97s, 86s, 75s, 64s, 53s, 42s (about half of the suited gappers)
• Some suited broadways: A2s-A5s already included; additionally JTs, QTs, KTs can be added (but KTs is already in KX suited)
• Some connectors: T9s, 98s, 87s (already included in suited connectors); also consider K9s, Q9s, J8s etc. (optional)

Overall, a typical CO opening range represents about 20%-22% of all hands, i.e., roughly 260-280 combinations.

Range Construction Logic

1. Value/bluff balance: Core value hands include strong pairs (TT+) and strong AX (AJ+), which have equity advantage against the blinds' calling ranges. Bluffing hands consist of small pairs (22-99) and suited connectors/gappers, which have postflop playability (draw potential).
2. Maximizing positional advantage: The CO can see all actions except the BTN, so it can open wider than early positions while avoiding early squeezes. Suited connectors and gappers in the range can easily form straight or flush draws postflop; even if they miss, position can be used to steal pots.
3. Exclusion: Avoid over-including hands that are vulnerable to re-raises and squeezes, such as KJo, QTo and other offsuit middle hands, which are difficult to play postflop.

Adjustment Factors

• Blind player style: If the blinds are very loose-aggressive, tighten the range (remove the bottom 20% of hands). If the blinds are passive, widen to about 25% by adding more suited gappers and some offsuit connectors (e.g., 97o).
• Button tendency: If the BTN frequently 3-bets, prioritize strong value hands and reduce easily-foldable bluff hands (e.g., 54s). If the BTN often folds, expand the range.
• Stack depth: With short stacks (<40BB), adopt a more push/fold strategy, focusing on high pairs and strong AX, and reduce suited connectors. With deep stacks (>150BB), increase the weight of suited connectors and gappers to utilize implied odds.
• Limpers: If there are limpers, raise to isolate, but use a slightly stronger range than standard (eliminate the weakest isolation hands like 42s).

GTO Reference

In GTO (Game Theory Optimal) strategy, the CO opening frequency is about 20%-23%, depending on table dynamics. In theory, the CO's range should make the blinds' EV of calling and 3-betting roughly equal. Typical GTO solver outputs are similar to the above recommendation but assign mixed frequencies to certain hands (e.g., KJo split between raising and folding).

• Raise size: Usually standard 2.5-3BB. If the blinds 3-bet frequently, increase the raise size to 3-3.5BB to reduce implied odds.
• Response to 3-bets (GG strategy): Use value hands (QQ+, AK) for 4-bet, mid-strength hands (TT-JJ, AQ) for calling, and weak hands (small pairs, suited connectors) for folding. Adjust based on opponent tendencies.

Practical Application

1. Steal opportunities: When the blinds fold often, widen the CO range to about 30%, including all suited aces, all suited kings, all pairs, and some suited connectors (e.g., 53s).
2. Information exploitation: Observe the BTN's 3-bet tendency. If the BTN rarely 3-bets, open with a wider range confidently. If the BTN squeezes frequently, consider slow-playing strong hands like TT+, AJ+ to avoid being bluffed.
3. Postflop strategy: Since the CO range includes many suited connectors, the continuation bet frequency is high when hitting strong pairs or draws. On dry flops (e.g., K72 rainbow), c-bet at high frequency. On wet flops (e.g., 89T two-suited), be cautious and consider checking to control the pot.
4. Range adjustment example: Suppose you hold A2s in the CO. Under standard conditions, you raise. But if the BTN is an aggressive 3-bettor, you might fold (since A2s is difficult to play against a 3-bet). Conversely, if the blinds are very loose, A2s remains a good raise because it can easily form flush draws postflop.

In summary, the CO's opening range should be adjusted flexibly based on opponents and dynamics. Remember the core principle: positional advantage allows you to play more hands, but also avoid being exploited in return.