Abstract: The center distance of a roller chain drive greatly affects kinematics and dynamics in chain drives. Dichotomy method is given to calculate the center distance of a roller chain drives more accurately than the existing methods. When the length of chain is an even number of chain pitches, the maximum and minimum values of center distances of a roller chain drives calculated with dichotomy method are almost the same as those by the Winklhofer method and compatible of with involute function method. The Winklhofer method is an exact method. But Winklhofer method cannot calculate center distance of a roller chain drive whose length of chain is an odd number of chain pitches. Involute function method is an approximative method. The Involute function method cannot calculate center distances of a roller drive exactly. Dichotomy method is a numerical method. Dichotomy method can calculate center distances of a roller drives. Dichotomy method can be used in a chain drive whose length of chain is any value. The accurate dichotomy method is significant for a roller chain drive whose distance cannot be adjusted and for shafts on which there is more than one roller chain drive.