True Count

Divide the Running Count by the decks remaining. That is the True Count, the number that sets your bet, your Index Plays, and your insurance decision. Each point of True Count is worth about half a percent of edge. The house starts about half a percent up, so the crossover is near true +1. Below it you are the underdog. Above it the casino is. At true +3 you play with roughly a 1% edge, which is more than the house usually has on you.

This Course teaches and grades one convention, truncate toward zero. Running +9 with 2.5 decks left is 3.6, so call it +3. Running −7 with 2 decks is −3.5, so call it −3. Truncation is conservative on purpose. Rounding down on positive counts means you never bet edge you do not have, and rounding toward zero on negative counts never makes you leave a shoe faster than the math demands. Some books round to the nearest half. Pick one convention and keep it.

Work these at the speed you will face them, between the dealer's shuffle glance and your bet. +8 with 4 decks is 2. +7 with 2 decks is 3, since 3.5 truncates. −5 with 1.5 decks is −3, since −3.33 truncates. +3 with 5 decks is 0. Early in a big shoe, a nice Running Count usually means nothing yet.

The arithmetic has to be instant and silent. If division under pressure is shaky, practice the common denominators until the answers come on their own. Dividing by 1.5 is two-thirds. Dividing by 2.5 is times four, then divide by 10.