The Biggest Preflop Mistakes in Poker

Preflop decision-making in poker establishes the foundation for all subsequent betting rounds. Errors made before the flop often propagate into compounded strategic disadvantages, leading to significant losses in expected value (EV). Drawing on cognitive science, probability theory, and strategic game analysis, this article identifies the most common preflop mistakes made by players across skill levels. By framing these mistakes within behavioral and decision-making research, the study offers evidence-based recommendations for improvement.

Despite its seemingly simple nature, preflop play requires balancing game-theoretic principles with exploitative adaptations. Research in strategic decision-making highlights that errors made early in a decision tree magnify downstream costs (Kahneman & Tversky, 1979). This article examines the most significant categories of preflop mistakes and situates them within cognitive and probabilistic frameworks.

This article examines the six most consequential categories of preflop mistakes, situating them within frameworks of probability, behavioral science, and equilibrium game theory. Each mistake is explored in depth with both theoretical discussion and practical methods for correction.

• Mistake 1: Playing Too Many Hands
• Mistake 2: Ignoring Position
• Mistake 3: Improper Open Sizes
• Mistake 4: Incorrect 3-Betting Frequency
• Mistake 5: Failing to Adjust for Stack Depth
• Mistake 6: Cold Calling Too Frequently

Mistake 1: Playing Too Many Hands

From a purely mathematical perspective, each starting hand has an associated equity distribution across common ranges. Game-theoretic models show that many hands—especially offsuit, uncoordinated ones—carry negative EV when played too frequently from most positions. The profitability of preflop play stems not from the raw equity of the hand alone, but from range construction, positional advantage, and playability postflop.

Solver analysis indicates:

• Hands such as offsuit gappers (e.g., J4o, T6o) are nearly always folds, regardless of position.
• Many suited hands (e.g., 65s, A5s) enter profitable ranges primarily due to their postflop playability and equity realization in position.
• A solver’s opening range tightens dramatically in early positions and expands progressively by the cutoff and button.

Psychological Basis

Overplaying weak hands often results from availability bias and illusion of control:

• Availability bias: Players recall rare instances when J4o cracked aces and overestimate its profitability.
• Illusion of control: Players believe superior postflop skill compensates for weak preflop ranges, even though math dictates consistent disadvantages.

This mirrors decision-making errors in other domains, where individuals overweight salient outcomes and underweight probabilistic base rates.

Consequences in Practice

• Equity disadvantage: Entering pots with weak holdings lowers win probability against standard opening ranges.
• Reverse implied odds: Hands like KJo often make second-best holdings, leading to larger losses.
• Cognitive overload: Playing too many hands creates complex postflop scenarios, increasing the likelihood of additional mistakes.

Practical Drills

1. Range Discipline Exercise
   • Use tracking software to filter hands by position.
   • Identify instances of hands played outside of a standard solver-approved range.
   • Tag these hands for review, noting both EV loss and alternative fold/raise options.
2. Equity Familiarization
   • Run equity simulations in software such as PokerStove or Equilab.
   • Compare “fun-looking” hands (e.g., J8o, T7o) against standard opening ranges.
   • Record win rates and use this as a mental anchor to resist over-involvement.
3. Tightness Drill
   • For one session, deliberately play 20% fewer hands than your usual frequency.
   • Track whether reduced involvement increases EV and lowers variance.

Mistake 2: Ignoring Position

Position is one of the most fundamental variables in poker strategy. Acting later in the betting sequence provides an information advantage, allowing a player to observe opponents’ actions before making their own decision. Game-theoretic solvers consistently show that the profitability of playable hands expands dramatically from early to late position.

For example:

• Under the gun (UTG), solver ranges recommend opening only ~15–18% of hands in a 6-max format.
• On the button, that range can expand to ~45–55%, nearly three times as wide.

This difference highlights how positional leverage multiplies expected value (EV). Hands that are -EV to play from early position can become strongly +EV when played in position.

Mathematically, position increases equity realization: the proportion of theoretical equity a hand actually captures in practice. Even marginal holdings like T8s or A5o realize far more equity on the button compared to early position.

Psychological Basis

Ignoring position stems from several well-documented cognitive biases:

• Egocentric bias (Pronin, 2008): Players overestimate their skill and assume they can “outplay” opponents regardless of informational disadvantage.
• Illusion of symmetry: Players treat situations as equivalent across positions, misapplying late-position strategies to early spots.
• Outcome bias: Winning a hand from early position with weak holdings reinforces the false belief that position is less important.

These biases lead to systematically overplaying hands in early and middle positions, where the EV loss compounds over large samples.

Consequences in Practice

• Range imbalance – Overly wide early-position ranges become vulnerable to 3-bets and squeezes.
• Capped equity – Weak hands played out of position rarely realize full equity, leading to negative EV across postflop streets.
• Increased cognitive strain – Navigating postflop spots without informational advantage requires higher skill, but many players underestimate this complexity.
• Downstream leaks – Overplaying early hands skews perception of variance, as losses appear to result from “bad luck” rather than structural positional errors.

Solver Insights

Solver outputs highlight dramatic EV differences:

• UTG open with 76s = near breakeven or -EV in solver equilibrium.
• Button open with 76s = clearly +EV, often ~+0.5 big blinds per 100 hands.

This demonstrates how the same hand transitions from a fold to a profitable raise purely based on position.

Practical Drills

1. Positional Range Mapping
   • Print or load solver-approved ranges for each position (UTG, MP, CO, BTN, SB, BB).
   • For one week, strictly adhere to these ranges.
   • Track discipline: note every deviation and whether it was profitable or not.
2. Equity Realization Exercise
   • Run equity simulations (e.g., Equilab) for the same hand against a standard opening range.
   • Compare outcomes in position vs. out of position.
   • Example: A5s vs. CO open → +EV on BTN, often -EV in blinds.
3. Single-Position Sessions
   • Dedicate one session to focusing exclusively on play from one position.
   • Review all hands afterward, noting EV differences compared to other positions.
   • Over time, this builds intuition for the relative strength of ranges.

Conclusion

Ignoring position is one of the most costly preflop mistakes, as it undermines the structural advantages that drive long-term profitability. By recognizing cognitive biases, studying solver-based ranges, and implementing positional drills, players can correct this leak. Proper positional discipline not only increases EV but also simplifies postflop decision-making, reducing cognitive strain and variance.

Mistake 3: Improper Open Sizes

The size of a preflop open raise is a crucial determinant of range construction, pot odds offered, and subsequent postflop dynamics. Optimal sizing balances risk versus reward: raising large enough to generate fold equity and deny opponents’ equity realization, while small enough to risk fewer chips and preserve maneuverability.

Solver outputs consistently recommend moderate open sizes in most no-limit hold’em formats:

• Online 6-max cash games: 2.0–2.5 big blinds (bb).
• Live cash games: often slightly larger (2.5–3bb) due to looser field tendencies.
• Tournaments: depth-dependent, but typically 2–2.2bb at <50bb effective stacks.

Deviating substantially from these baselines either inflates variance (too large) or reduces fold equity (too small).

Psychological Basis

Improper open sizing is driven by several biases:

• Anchoring bias (Tversky & Kahneman, 1974): Many players adopt arbitrary “standard” sizes (e.g., always 3x) without considering evolving theory or stack dynamics.
• Illusion of protection: Some players raise excessively large, believing this “protects” their hand from being outdrawn, ignoring that they also risk unnecessary chips.
• Overconfidence bias: Players believe they can outplay opponents postflop regardless of pot size, leading to erratic sizing.

These tendencies lead to systematic EV loss across thousands of hands.

Consequences in Practice

1. Overly large open sizes
   • Risk excessive chips relative to the pot.
   • Reduce maneuverability postflop with medium stacks.
   • Create exploitable patterns (opponents tighten ranges excessively and fold too often).
2. Overly small open sizes
   • Offer attractive pot odds, inviting multiway pots.
   • Reduce fold equity against blinds.
   • Allow opponents to realize equity cheaply with speculative holdings.
3. Inconsistent sizing
   • Telegraphed hand strength (e.g., larger opens with premiums, smaller with marginal hands).
   • Enables opponents to exploit via range narrowing.

Solver Insights

Solver simulations show:

• At 100bb effective stacks in 6-max cash:
  • UTG 2.0–2.3bb open yields EV within 0.1bb/100 of equilibrium optimum.
  • UTG 4bb open increases variance significantly while lowering long-term EV.
• On the button:
  • 2bb open forces blinds to defend very wide ranges.
  • 3.5bb open reduces button’s EV due to excessive chip risk.

Thus, solvers optimize around consistent, moderate open sizes that maintain balance and exploit opponents’ forced defense ranges.

Practical Drills

1. Standardization Exercise
   • Select one open size (e.g., 2.2bb online cash, 2.5bb live).
   • Play 5,000 hands using this as a baseline across all positions.
   • Review outcomes, comparing variance and EV to prior play.
2. Pot Odds Simulation
   • Use a calculator to determine pot odds offered by various open sizes.
   • Example: 2bb open in 6-max → blinds need ~20% equity to call.
   • Contrast with 3.5bb open → blinds need ~27%.
   • Observe how smaller sizes incentivize wider calls.
3. Exploitative Adjustment Drill
   • Identify table types:
     • Tight blinds → smaller open sizes are optimal (less resistance).
     • Loose, sticky blinds → larger opens (2.5–3bb) regain fold equity.
   • Practice dynamically adjusting sizing to opponent tendencies while maintaining consistency within a session.

Conclusion

Improper open sizing is a fundamental preflop leak that distorts ranges, creates exploitability, and increases variance unnecessarily. By grounding open sizes in solver-based recommendations, avoiding psychological biases, and practicing standardized drills, players can optimize their preflop strategy. Consistent, depth-aware open sizing maximizes fold equity, reduces variance, and strengthens range balance across positions.

Mistake 4: Incorrect 3-Betting Frequency

The 3-bet (re-raising an open raise) is one of the most powerful tools in preflop poker. Correctly applied, it accomplishes three strategic objectives:

1. Value extraction – maximizes EV with premium hands against wider opening ranges.
2. Fold equity – forces opponents to fold marginal hands, capturing dead money.
3. Range protection – prevents one’s range from becoming too passive and capped.

Game-theoretic solvers recommend mixed 3-bet strategies that blend strong value hands with carefully chosen bluffs (often using blocker properties). For example:

• UTG vs. CO open (6-max, 100bb): 3-bet range = QQ+, AK (value) + A5s, KTs, 76s (bluff).
• Button vs. CO open: wider 3-bet range = TT+, AQ+, A2s–A5s, suited broadways, occasional suited connectors.

Deviation from these frequencies either leads to under-3-betting (too passive, exploitable by aggressive opponents) or over-3-betting (too aggressive, bleeding chips with dominated bluffs).

Psychological Basis

Cognitive and behavioral biases drive incorrect 3-betting frequencies:

• Risk aversion → under-3-betting: Players prefer calling to “see a flop” rather than risking more chips with re-raises.
• Overconfidence & illusion of control → over-3-betting: Players believe they can outplay opponents postflop even with weak hands, leading to excessive bluff 3-bets.
• Loss aversion (Kahneman & Tversky, 1979): Fear of building a large pot and losing discourages optimal aggression.

These tendencies distort preflop ranges and make players predictable.

Consequences in Practice

1. Under-3-Betting (Too Passive)
   • Opponents open wider ranges uncontested.
   • Hero becomes capped, with fewer premiums in range.
   • Reduced fold equity and weaker positional leverage.
2. Over-3-Betting (Too Aggressive)
   • Excess chip loss with unsound bluffs.
   • Excess chip loss with unsound bluffs.
   • Creates exploitable imbalance opponents can adjust to by widening 4-bet ranges.
3. Unbalanced Distribution
   • Only 3-betting value hands makes the range transparent.
   • Only 3-betting bluffs loses significant EV with premiums.

Solver Insights

Solver outputs illustrate the importance of frequency balance:

• BTN vs. CO open (100bb):
  • Solver 3-bets ~12–15% of hands.
  • Balanced mix: ~8% value, ~7% bluffs.
• SB vs. BTN open (100bb):
  • Solver 3-bets ~16–20%.
  • Higher aggression required due to positional disadvantage.

This balance ensures opponents cannot profitably call or fold too frequently, keeping strategies near equilibrium.

Practical Drills

1. Range Construction Drill
   • Build 3-bet ranges by position using solver charts or preflop trainers.
   • Separate into value (e.g., QQ+, AK) and bluff (blocker-heavy, suited connectors) components.
   • Practice recognition of these categories in hand reviews.
2. Frequency Tracking
   • Use database software (e.g., PokerTracker, Holdem Manager) to monitor your 3-bet %.
   • Compare actual frequencies to solver recommendations:
     • BTN vs. CO: ~12–15%.
     • SB vs. BTN: ~16–20%.
   • Identify whether you are under- or over-3-betting.
3. Flashcard Simulation
   • Create flashcards with random preflop situations (e.g., “BTN vs. CO open, 100bb, hand = A5s”).
   • Practice deciding: fold, call, 3-bet.
   • Check against solver ranges until decisions become automatic.

Conclusion

Incorrect 3-betting frequency represents a critical preflop leak, either through excessive passivity or over-aggression. Both reduce EV by allowing opponents to exploit imbalanced ranges. By understanding solver-approved frequencies, identifying psychological biases, and drilling range recognition, players can calibrate their aggression levels. Balanced 3-betting not only maximizes immediate fold equity but also preserves long-term range protection, keeping opponents guessing and ensuring sustainable profitability.

Mistake 5: Failing to Adjust for Stack Depth

Effective stack depth fundamentally alters the profitability of preflop decisions. Strategic adjustments are required because stack size determines:

1. Implied odds – potential payoff when speculative hands (e.g., suited connectors, small pairs) hit strong postflop holdings.
2. Fold equity – the leverage generated by raises or shoves.
3. Commitment thresholds – how quickly a pot becomes “all-in relevant.”

Solvers consistently demonstrate that preflop ranges must narrow or expand depending on stack depth:

• Shallow stacks (<30bb): Favor linear, value-heavy strategies. Speculative calls (e.g., 76s, 22) lose profitability due to insufficient implied odds.
• Medium stacks (30–70bb): Hybrid play with adjusted 3-bet sizing and selective flatting.
• Deep stacks (>100bb): Broader ranges that include speculative holdings (suited connectors, suited gappers, small pairs) due to higher implied odds and maneuverability.

Psychological Basis

Many players fail to adapt because of anchoring bias—defaulting to “standard” preflop ranges irrespective of stack depth. Other cognitive factors include:

• Status quo bias: Preference for familiar routines (“I always open this hand from the cutoff”).
• Loss aversion: Overfolding in shallow stacks due to fear of busting, even when shoves are +EV.
• Illusion of safety: Calling too wide with deep stacks, believing implied odds always justify speculative play.

These biases create systematic leaks across stack depths.

Consequences in Practice

1. Shallow Stacks (<30bb)
   • Calling with speculative hands (e.g., 22, 65s) without sufficient implied odds.
   • Overfolding profitable shove ranges in tournaments.
   • Using non-all-in 3-bets that pot-commit without fold equity.
2. Medium Stacks (30–70bb)
   • Misapplying deep-stack ranges (e.g., flatting too wide in blinds).
   • Failing to adjust 3-bet sizes, leaving exploitable patterns.
3. Deep Stacks (>100bb)
   • Overcommitting with top pair / overpair hands, which lose relative value.
   • Underutilizing speculative hands that benefit from implied odds.

Solver Insights

• 20bb BTN vs. CO open (tournament setting): Solver prefers shove-or-fold strategies, removing marginal flat calls.
• 100bb CO open vs. BTN: Solver includes suited connectors (65s–T9s), suited aces, and small pairs due to implied odds.
• 200bb deep cash game: Solver dramatically widens 3-bet ranges with suited connectors and adds more mixed-strategy hands, but reduces commitment with one-pair holdings.

Thus, stack depth not only changes the range composition but also the relative strength hierarchy of hands.

Practical Drills

1. Stack-Depth Simulation
   • Run solver scenarios at 20bb, 50bb, 100bb, and 200bb.
   • Record differences in recommended open and 3-bet ranges.
   • Build a comparative chart for reference during play.
2. All-In Threshold Drill
   • For short stacks, review shove-or-fold charts.
   • Practice recognizing automatic shoves (e.g., 15bb BTN shove with A7s).
   • Quiz yourself to internalize profitable thresholds.
3. Deep Stack Awareness
   • Review 5 hands played at >150bb.
   • Identify whether you overcommitted with marginal top pairs.
   • Replace these hands with solver-preferred lines (e.g., more controlled pot sizes).

Conclusion

Failure to adjust for stack depth is a major preflop leak that distorts ranges and misapplies strategic principles. Shallow stacks demand simplified, linear aggression; medium stacks require nuanced adjustments; deep stacks encourage speculative range expansion while demanding postflop caution. By studying solver outputs and practicing depth-specific drills, players can avoid anchoring bias and develop flexible, adaptive strategies that maximize EV across varying stack conditions.

Mistake 6: Cold Calling Too Frequently

A cold call occurs when a player calls an opponent’s open raise without being in the blinds and without re-raising. While cold calling may occasionally be optimal (e.g., set-mining with small pairs or flatting strong hands in multiway-prone environments), solvers demonstrate that its frequency is far lower than many players assume.

The core issue: cold calling caps a range—excluding the strongest value hands (AA, KK, AKs) that are usually 3-bet—and introduces equity disadvantages by inviting multiway pots. Without initiative or the strongest hands in range, the cold caller enters the flop at a structural disadvantage.

Solver outputs confirm this:

• In 6-max, 100bb cash games, cold calling ranges are often extremely narrow outside of the big blind (BB).
• On the button, solvers may allow some flats versus a CO open (e.g., 99, AJs, KQs), but even here 3-betting is often preferred.
• In the small blind, cold calling ranges shrink dramatically due to positional disadvantage, with solvers favoring 3-bets or folds.

Psychological Basis

Frequent cold calling stems from predictable cognitive biases:

• Loss aversion: Calling feels safer than risking more chips with a 3-bet or folding a playable hand.
• Illusion of postflop edge: Players overestimate their ability to outplay opponents postflop with hands like QJs or 55.
• Sunk cost fallacy: After investing blinds, players justify looser calls to “defend what they’ve already put in.”

These biases create bloated pots where the cold caller’s range is structurally capped and vulnerable.

Consequences in Practice

1. Capped Ranges
   • Strongest hands missing → opponents can pressure capped ranges postflop.
   • Leads to difficulty defending against barrels and squeezes.
2. Equity Disadvantage in Multiway Pots
   • Cold calls invite squeezes from aggressive players behind.
   • Realization of equity drops sharply without initiative.
3. Reduced Fold Equity
   • Calling instead of 3-betting removes the chance to win immediately.
   • Blinds and overcallers gain favorable odds, worsening the cold caller’s position.

Solver Insights

• BTN vs. CO open (100bb): Solver cold calls ~6–8% of hands (AJs, KQs, some pocket pairs). Most hands shift into 3-bets or folds.
• SB vs. BTN open (100bb): Solver cold calls <3% of hands; vast majority are folds or 3-bets.
• BB vs. open: Solver defends widely (~40–50%) but this is not “cold calling” since blinds already have money invested.

Thus, cold calling is situational and narrow, not a default line.

Practical Drills

1. Database Filter Review
   • Use tracking software to filter for “cold calls.”
   • Examine profitability by hand class (suited connectors, small pairs, offsuit broadways).
   • Compare actual results to solver-approved ranges.
2. Squeeze Awareness Drill
   • Identify hands where you cold called and then faced a squeeze.
   • Note how often these spots forced folds, costing chips unnecessarily.
   • Replace with solver-preferred 3-bets or folds.
3. Position-Based Range Adjustment
   • Create separate charts for cold calls from BTN, SB, and BB.
   • Practice by position, ensuring cold calls remain narrow and supported by solver data.

Conclusion

Excessive cold calling is one of the most common preflop leaks, rooted in loss aversion and overconfidence. By capping ranges, inviting squeezes, and reducing fold equity, habitual cold calling significantly lowers long-term EV. Solvers confirm that cold calling should be highly selective, used only in specific contexts where range construction and pot dynamics justify it. Through disciplined range construction, database review, and positional drills, players can replace weak calls with strategically stronger folds or 3-bets, strengthening both preflop and postflop play.

References

• Kahneman, D., & Tversky, A. (1979). Prospect theory: An analysis of decision under risk. Econometrica, 47(2), 263–291.
• Pronin, E. (2008). How we see ourselves and how we see others. Science, 320(5880), 1177–1180.
• Tversky, A., & Kahneman, D. (1973). Availability: A heuristic for judging frequency and probability. Cognitive Psychology, 5(2), 207–232.
• Tversky, A., & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124–1131.
• Von Neumann, J., & Morgenstern, O. (1944). Theory of Games and Economic Behavior. Princeton University Press.