Poker Math Trainer

Why these four formulas

Almost every in-game maths decision in poker comes down to one of four calculations: how likely you are to improve, what equity a call needs, how often you must defend against a bet, and whether a decision is profitable overall. Learn these four and you can work out the right answer at the table without memorising a single hand.

Related pages

• Equity Calculator →
• Pot Odds Calculator →
• MDF lesson: bluff catching →
• Equity lesson →
• Pot odds lesson →

Frequently asked questions

What is the rule of 2 and 4 in poker?

A quick way to turn an outs count into an equity estimate without running a full equity calculation. With two cards to come, multiply your outs by 4; with one card to come, multiply by 2. Nine outs (a flush draw) is roughly 36% on the flop and 19% on the turn.

Why does the rule of 4 overstate equity with a lot of outs?

It is a linear approximation of a curve that flattens out as outs increase, so it gets less accurate the more outs you have. A 15-out combo draw is closer to 54% by the river than the 60% the rule of 4 suggests. Past about 8 outs, subtract 1% for every out over 8 to correct for this.

What is the formula for pot odds?

Required equity = bet / (pot + bet). If your real chance of winning is above that number, calling is profitable in the long run; if it is below, folding is.

What is minimum defence frequency (MDF)?

The smallest share of your range you must continue with against a bet so the bettor cannot show an automatic profit by bluffing any two cards. It is calculated as pot / (pot + bet), the mirror image of the pot odds formula.

Is MDF the same as pot odds?

No. Pot odds tell you the equity one specific hand needs to call profitably; MDF tells you how much of your whole range must continue. They share the same formula shape, bet vs pot, but answer different questions.

How do you calculate the EV of a poker decision?

EV = (probability of winning × amount won) − (probability of losing × amount lost). A decision is profitable in the long run whenever its EV is positive, whatever the outcome of any single hand.

Do I need to memorise these formulas at the table?

Not exactly, but the shortcuts on this page (rule of 4, common pot odds ratios, standard MDF percentages) are worth memorising, since deriving them from scratch mid-hand is too slow. The drill on this page is built to help that stick.

What is a combo draw and why does it change the maths?

A combo draw is two draws at once, most often a flush draw plus a straight draw, so its outs add together (a flush draw plus an open-ended straight draw is often 15 outs). Because the rule of 4 overstates equity for large out counts, combo draws are exactly where the correction matters most.

Is this different from the Equity Calculator or Pot Odds Calculator?

Those two tools solve one specific hand exactly, given real cards or ranges. This page is a reference and drill for the underlying formulas, including MDF and EV, which neither calculator covers on its own.

Is this free to use?

Yes, the cheat sheet and drill are free with no sign-in and no limit. The ranked Trainer, which grades full hand decisions and adapts to your rating, is a separate subscription with a 14-day free trial.