3-Bet Defense Calculator
Use this calculator to determine your minimum defense frequency (MDF) when facing 3-bets in Texas Hold'em. Understanding how often you need to continue against re-raises is essential for preventing opponents from profitably bluffing you with any two cards. This tool helps you build mathematically sound defense strategies based on pot odds and 3-betting theory.
Calculate Your Defense Frequency
Defense Analysis
Pot Math Breakdown
💡 Strategy Recommendation
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MDF tells you the theoretical minimum defense to prevent pure bluff exploitation. In practice, defend less than MDF against tight 3-bettors and consider defending more when you have position and playable hands. Your actual equity when called matters more than hitting exact MDF numbers.
Custom Scenario Analysis
Compare how different 3-bet sizes affect your required defense frequency. Enter your open raise and blinds, then see the MDF for various 3-bet sizes.
3-Bet Size Comparison
Understanding Minimum Defense Frequency
Minimum Defense Frequency (MDF) is a fundamental concept in game theory optimal (GTO) poker that determines how often you must continue with your range to prevent opponents from profitably bluffing with any two cards. When facing a bet or raise, folding too frequently allows aggressive opponents to exploit you by betting relentlessly, winning the pot unchallenged.
The MDF formula is elegantly simple: MDF = Pot Size ÷ (Pot Size + Bet Size). Alternatively, you can express this as MDF = 1 - (Bet Size ÷ Total Pot After Bet). Both formulas yield the same result—the percentage of your range that must continue (by calling or raising) to make your opponent's pure bluffs break even.
How 3-Bet Sizing Affects Your Defense
The size of the 3-bet dramatically impacts how wide you can profitably defend. According to research published by the PokerStrategy education platform, smaller 3-bet sizes require you to defend wider ranges, while larger sizes allow more folding without exploitation. A 3x 3-bet (e.g., 9bb over a 3bb open) typically requires approximately 55-60% defense, while a 4x 3-bet might only require 45-50%.
However, MDF provides a theoretical ceiling, not a mandate. In real games, most opponents don't 3-bet bluff optimally. If villain rarely 3-bet bluffs, you can profitably fold more than MDF suggests. Understanding your opponent's tendencies through observation and tracking software is crucial for adjusting your defense frequencies appropriately.
Position and Defense Strategy
Your position relative to the 3-bettor significantly impacts how you should construct your defense range. When defending in position (IP), you have a significant post-flop advantage: you act last on every street, can control pot size more effectively, and realize your equity more efficiently. This positional advantage justifies defending wider than MDF might suggest—often 50-60% of your opening range against standard 3-bet sizes.
Out of position (OOP), the calculus shifts dramatically. The positional disadvantage means you'll lose more pots post-flop even with decent hands. Upswing Poker's research suggests defending only 35-45% of your opening range against 3-bets when OOP, well below the mathematical MDF. The equity loss from position often outweighs the theoretical exploitation loss from folding more.
Building Your Defense Range
A solid 3-bet defense strategy divides your continuing range into three categories:
- Premium 4-bet hands: AA, KK, QQ, AKs, and sometimes JJ/AKo form your value 4-betting range. These hands perform well in 4-bet pots and can stack off preflop profitably.
- Calling hands: Strong suited hands (AQs, AJs, KQs), pocket pairs (99-JJ), and suited connectors that play well post-flop. These hands have good playability but don't want to build massive pots preflop.
- Bluff 4-bets: Hands like A5s, A4s, K5s that have blockers to premium hands and some equity when called. These balance your 4-betting range so you're not always value-heavy.
Common Adjustments to MDF
Pure MDF calculations assume optimal opponent play, but real poker involves significant adjustments. Here are key factors that should modify your defense frequencies:
Stack Depth: With 100bb+ effective stacks, you have more room to maneuver post-flop, making speculative hands more valuable. With shorter stacks (under 40bb), the tournament dynamics often favor either folding or 4-bet shoving rather than flat calling.
Opponent Tendencies: Against a player who only 3-bets premium hands (AA, KK, QQ, AK), your defense frequency should plummet regardless of MDF. Against someone who 3-bets liberally with suited connectors and suited aces, you must defend at or above MDF.
Tournament Considerations: In ICM situations, chip preservation becomes paramount. Near the money bubble or at final tables with significant pay jumps, folding more than MDF is often correct because the risk of elimination outweighs the EV loss from folding "exploitably."
The Relationship Between MDF and Pot Odds
MDF and pot odds are mathematically related but serve different purposes. Pot odds tell you the minimum equity needed to call profitably, while MDF tells you the minimum frequency to defend to prevent exploitation. When you're getting 2:1 pot odds (need 33% equity), your MDF is also about 67%. The concepts converge but apply differently—pot odds apply to individual hands, while MDF applies to your entire range.
Understanding this distinction is crucial for advanced play. According to the CardPlayer odds guide, you might have a hand with only 30% equity against villain's 3-betting range, making it an unprofitable call based on pot odds alone. However, you might still include it in your calling range because your overall defense frequency would drop too low without it, allowing villain to bluff profitably.
Frequently Asked Questions
What is minimum defense frequency (MDF) in poker?
Minimum defense frequency is the percentage of hands you must continue with (call or raise) to prevent your opponent from profitably bluffing with any two cards. MDF is calculated as: Pot Size ÷ (Pot Size + Bet Size). If you fold more than 1 - MDF, your opponent profits by bluffing 100% of the time.
How do you calculate MDF against a 3-bet?
To calculate MDF against a 3-bet: First determine the total pot after the 3-bet (blinds + your open + villain's 3-bet), then use the formula MDF = Pot ÷ (Pot + Call Amount). For example, if you open to 3bb, villain 3-bets to 9bb with 1.5bb in blinds, the pot is 13.5bb and you need to call 6bb, giving MDF = 13.5 ÷ 19.5 ≈ 69%.
Should I always defend at exactly MDF against 3-bets?
No. MDF represents the theoretical maximum you can fold, not a target to hit exactly. In practice, defend less than MDF against tight 3-bettors who rarely bluff, and consider defending at or above MDF against aggressive players. Position also matters—defend tighter when out of position due to post-flop disadvantages.
What percentage of my opening range should I defend vs 3-bets?
Typical defense frequencies are 40-60% of your opening range in position, and 30-45% out of position. This varies based on 3-bet size, stack depth, and opponent tendencies. Against larger 3-bets, you can fold more; against smaller ones, defend wider.
Related Tools and Guides
Mastering 3-bet defense requires understanding several interconnected concepts. Explore these related tools and guides to deepen your knowledge:
- 3-Betting Strategy Guide - Comprehensive guide to offensive 3-betting, including when to 3-bet for value vs. bluff
- Pot Odds Calculator - Calculate pot odds for any situation to determine profitable calls
- Hand Range Visualizer - Build and analyze opening ranges by position
- Expected Value Calculator - Analyze the EV of calling, folding, or 4-betting against 3-bets
- Poker Position Explained - Understand why position matters so much when defending against 3-bets
Understanding 3-bet defense is a key step toward becoming a more balanced, unexploitable poker player. While the math provides a foundation, developing reads on your opponents and adjusting accordingly separates good players from great ones. Use this calculator to build your theoretical understanding, then refine your strategy through practice and observation at the tables.