Abstract: Disclosed is a system and method for determining an efficient and accurate committed information rate (CIR) for a frame relay data communications device to facilitate the conversion of frame relay data packets into asynchronous transfer mode (ATM) data cells. In one embodiment, the present system includes a processor coupled to a local interface, a memory coupled to the local interface, an adaptive CIR logic stored in the memory, the adaptive CIR logic being executed by the processor, the adaptive CIR logic including: sample identification logic to identify at least one sample group of a number of data packets transmitted across a data communications link, the data packets having a variable length and the data cells having a fixed length, modeling logic to adapt a modeled packet size of the frame relay data packets transmitted across the data communications link based upon the data packets in the sample group, and, logic to calculate an efficient committed information rate based upon the modeled packet size.