A current monitor includes current sense logic and a processor. The current sense logic senses inductor current at a predetermined time point during operation of a constant on-time regulator. The processor determines output current of the constant on-time regulator based on the inductor current sensed at the predetermined time point. The predetermined time point corresponds to half of an on-time period of the constant on-time regulator. The output current may be determined during continuous conduction mode (CCM) or discontinuous conduction mode (DCM). During DCM mode, the processor determines the output current of the constant on-time regulator based on a skip time.