Certain aspects and features relate to a system and a sensor that provides real-time, downhole cutting concentration measurements. Electrical impedance measurements can be used in conjunction with a wired drill pipe to monitor the drill cuttings in the annulus under downhole conditions and along the drill string. This measurement provides direct information for optimal cuttings cleaning efficiency. In some examples, the system includes the sensor, a processing device connected to the sensor, and a non-transitory memory device including instructions that are executable by the processing device to cause the processing device to apply a transmitted signal to the sensor, receive an impedance signal from the sensor, and correlate the impedance signal with a wellbore cuttings concentration. In some examples the sensor includes multiple electrodes attachable to a drill string.