50 + D*85/(T+6)
To anyone who takes the game seriously and is of a certain age (like me) this formula will be etched in their memory. For the uninitiated, the “Janowski formula” enables one to calculate to a good approximation the probability of winning a match from any given score. This formula helps one to recreate a match equity table (MET) which can then be used to work out doubling and take points. I came across it for the first time in Kit Woolsey’s How to play Tournament Backgammon. I must have applied this formula OTB (over the board) more times than I have had hot dinners during my formative BG years living in Hong Kong, but I never knew who Rick Janowski was.