From The Backgammon Book, by Oswald Jacoby and John R. Crawford
double to 4?
Here is a simple rule for doubling in a running game:
- Count your position and your lead.
- If your lead is as much as 7½ per cent of your count, make a first double.
- If it is as much as 10 per cent of your count, make a first double or redouble.
- If your opponent doubles in a running game, accept any time you are less than 15 percent of your opponent’s count behind (i.e., his lead is less than 15 per cent).
Thus, in Diagram 39 your count is 109 and your lead over your opponent’s count (118) is 9; 9 is about 8¼ per cent of your count, so you should make a first double, but you should not make a redouble.