A formula for help making doubling decisions in pure race situations in backgammon games. It enhances the basic pip count by accounting for elements of checker distribution. It was devised by Dr. Edward O. Thorp.
Each player's Thorp count is his pip count, plus 2 for each of his checkers still on the board, minus 1 for each of his occupied home board points, plus 1 for each checker on his one-point. Then the player on roll increases his count by 10 percent if it is more than 30.
Dr. Thorp advises:
Double any time your count does not exceed the opponent's by more than 2;
Redouble any time your count does not exceed opponent's by more than 1;
Accept the double if your count does not exceed doubler's by more than 2.