A system for tracking anesthetic agent in a vaporizer reservoir includes a mass flow sensor configured to measure a flow rate entering or exiting a vaporizer chamber, a gas pressure sensor configured to measure a pressure of a mixed gas provided from the vaporizer chamber, a gas temperature sensor configured to measure a temperature of the mixed gas provided from the vaporizer chamber, and an agent time module executable on a processor. The agent time module is configured to calculate a remaining agent time based on at least the gas flow rate, the pressure of the mixed gas, the temperature of the mixed gas, and an anesthetic concentration in the mixed gas. The remaining agent time is then provided for display on a display device.