Blackjack True Count: The Formula That Sizes the Bet

The blackjack true count is the running count divided by the number of decks remaining in the shoe. It tells you the actual concentration of high cards in the cards left to be dealt, which is the number that drives your bet size and your deviation plays. The running count tells you what has happened. The true count tells you what is left.

The formula is short. The math is integer division. The mental work is fitting both halves of the calculation together at casino pace, with a chatty dealer, a drink in your hand, and a player to your right asking if she should split tens.

A counter who runs the Hi-Lo count perfectly but cannot convert to a true count is flat-betting through favorable shoes by accident. The running count without the conversion is a number with no weight behind it. A running count of +6 with one deck left is enormous. A running count of +6 with five decks left is barely positive. The true count is what tells the difference.

What is a blackjack true count?

A blackjack true count is the normalized version of the running count. A running count of +12 in a 6-deck shoe means something different at the start of the shoe than at the cut card. Without normalization, the bet sizing math goes off the rails. The true count fixes that.

The technical name is "true count per deck" because the convention divides by remaining decks rather than remaining cards. The reason: every true count point corresponds to roughly +0.5% edge for the Hi-Lo player. A true count of +2 puts the player at roughly breakeven against a 6D H17 DAS LS game. A true count of +4 puts the player at ~1.5% edge over the base -0.47% house edge. Those edge numbers are derived per-deck, not per-card, which is why the conversion uses decks remaining as the divisor.

The true count is the trigger for both the bet ramp and the deviation plays. The Illustrious 18 and Fab 4 indices are stated in true count units. Insurance becomes profitable at TC+3. 16 versus 10 becomes a stand at TC 0+. 12 versus 3 becomes a stand at TC+2. Every one of those decisions keys off the true count, never the running count.

For a beginner working through the underlying Hi-Lo system, the foundation is in the card counting high low post and the broader card counting basics reference. The true count is the last math step before you start sizing the bet.

The true count formula: running count divided by decks remaining

True Count = floor(Running Count / Decks Remaining)

That is the entire formula. Three variables. One division. The result is what tells you how to bet the next hand.

A worked example. You are at a 6-deck shoe. The first deal goes by and you have a running count of +8. The discard rack tells you roughly one deck has been played. Five decks remain. The true count is floor(8 / 5), which is 1. You are at TC+1, which is positive but not by enough to change the bet meaningfully under most ramps.

Another example. Same shoe, three deals later. Running count is +10. Discard rack shows roughly three decks played. Three decks remain. True count is floor(10 / 3), which is 3. You are at TC+3, which is the insurance threshold and meaningfully positive. Bet bigger. Take insurance if the dealer shows an ace.

The math is integer division. You drop the decimal. A running count of +5 with two decks left is floor(5 / 2) = 2, not 2.5 and not 3. The rounding question is the next section.

How to estimate decks remaining

Estimating decks remaining is the part of the conversion that takes the most practice. The running count is a number you carry in your head. Decks remaining is a number you have to read off the table.

Look at the discard rack. Most casino discard racks are clear acrylic with a slot that holds the discarded cards stacked vertically. Eyeball the height of the stack. Compare it to the height of one deck (roughly half an inch in a 52-card stack on a standard rack). Subtract from 6 (or 8, or 2, depending on game).

The working target: estimate the discard rack within a half-deck just by looking. Most counters get there with a week of focused drilling at home: a 52-card deck, a clear cup or rack, and a guess-and-check loop. Stack a random number of cards, guess the deck count, count to verify. Repeat until the eyeball estimate is within 0.5 every time.

Some casino racks have markings on the side that show deck increments. Use them when they are there. Not every property has them.

The estimation error compounds. A 0.5-deck error on a true count divisor of 3 versus 3.5 makes a true count of 4 read as 3, which is the difference between insurance-on and insurance-off at the table. The math is sensitive. The eyeball has to be sharp.

Why floor the true count, never round

Always floor the running count divided by decks remaining. Never round. The reason is the asymmetry of the EV cost.

Rounding up means betting more (or taking a deviation play) one count earlier than the math supports. The EV cost compounds at high spreads. Over a thousand hours that error costs real money. The math is published in Schlesinger's Blackjack Attack and the qfit deep-dive on calculating true counts covers the precision differences across counting variants.

Rounding down (flooring) means a slight under-bet on the borderline shoes. The EV cost is small and symmetric. The error is bounded. Flooring keeps you on the right side of the spread without sacrificing meaningful EV.

The practical version: a running count of +5 with two decks left is TC+2, not TC+3. A running count of +7 with three decks left is TC+2, not TC+3. A running count of +10 with four decks left is TC+2, not TC+3. Floor every time. The 0.5 you discard does not earn you EV. The 0.5 you fail to discard does cost EV.

Do not deviate from this. Some online forums recommend "rounding to the nearest whole number." That recommendation is wrong and the published math is on the floor side. Schlesinger, Wong, Snyder, and Griffin all use the floor convention.

True count and the bet ramp

The true count is the trigger for the bet ramp. The bet ramp is the entire engine of card counting. A counter who runs a perfect Hi-Lo count and a perfect true count conversion but flat-bets every hand has the same expected loss as a non-counter, plus a tax on attention. The count tells you what to do. The spread is what does it.

A realistic 1-8 spread tied to the true count at a 6D H17 DAS LS table with $10 minimum:

• TC 0 and below: $10
• TC+1: $30
• TC+2: $60
• TC+3: $100
• TC+4: $200
• TC+5: $300
• TC+6 and above: $600

That ramp pulls a clean Hi-Lo player to roughly +1.0 to +1.5% edge over the base -0.47% house edge, depending on penetration and ramp shape. Without the ramp, the math does not move. Without the true count, the ramp has no trigger. The three pieces work together or not at all.

If you are scared to spread, do not count. Train, build a bankroll, and come back when you can. The drilling that compresses the timeline is in the card counting practice drills reference. A real-time true count display in the trainer paired with prompted bet sizes is the drill that builds the nerve to push the chips out when the count does turn favorable.

The mistakes you cannot catch on yourself are always the expensive ones. Some counters discover that their actual bet at TC+4 is consistently half of what their ramp says it should be. A trainer that tracks the gap between prompted bet and chosen bet surfaces the problem. Beyond the trainer, having someone read the data alongside you (a coaching program for example) is the level above self-grading, because self-reported numbers are always smaller than the actual gap.

True count and Hi-Lo deviations

The Illustrious 18 plus Fab 4 indices are all stated in true count units. Insurance at TC+3. 16 versus 10 at TC 0+. 12 versus 3 at TC+2. 10,10 versus 5 at TC+5. The full list and the count where each play triggers is on the Wizard of Odds Hi-Lo page and in Schlesinger's Blackjack Attack.

The highest-value deviation is insurance at TC+3. Insurance is a -7% house edge sucker bet for non-counters. At TC+3 the deck composition shifts enough that the math flips. A counter who takes insurance at TC+3 and refuses it below picks up meaningful EV per hour at heavy spreads. That single deviation is worth roughly 0.5% of the total counting edge depending on game rules.

Skipping deviations is paying for the count without using it. A counter who runs the perfect true count but always hits 16 versus 10 because "feels wrong" is leaking real EV. The chart says hit at TC negative. The chart says stand at TC 0+. Same hand, different count, different play. The shoe composition changed. The math changed. The play has to change with it.

The mechanical version of drilling deviations: trigger them under shoe conditions, not as flashcards in isolation. The transition you want is from "what does the chart say at this count" to "the count is +4, I have 15 versus 10, stand." The free CountEdge trainer drills the I18 and Fab 4 tied to the running count, with the true count surfaced or hidden depending on what you are training. No credit card. The About page covers why CountEdge exists at all: nothing on the market was good enough for a working counter to use. The true count math is settled. The drilling is what makes it pay.