An ink jet printer includes an ink supply system and a printhead with nozzles for ejecting ink drops. The printer determines the average size of the ejected ink drops by comparing the number of ink drops ejected in a predetermined time with the quantity of ink delivered through the printers ink supply system during that time. If the determined average ink drop size does not match predetermined ink drop size criteria, the printer adjusts the activation signals for the ink jet nozzles to alter the ink drop size. A solid ink printer determines the quantity of ink delivered through the ink supply system by counting the number of whole or partial ink sticks that pass a predetermined point in the ink supply system. The counter detects a sensing element formed on an external surface of the ink stick. Exemplary detectors include a mechanical arm, or a thermistor to detect a change in the printer melt plate temperature due to a change in the cross sectional area of an ink stick being melted.