A device and method for measuring a volume of liquid expelled from a syringe is provided. The device generally includes a syringe barrel, a plunger actuated with a plunger rod, and a sensor. The sensor may include two ports with one port being in fluid communication with a source of fluid external to the syringe barrel, while the second port is in fluid communication either with a proximal end portion of the syringe barrel or a hollow plunger rod having a first end closed by the plunger. The method may include expelling liquid from the syringe; detecting and recording differential pressure with the sensor over time; and calculating the volume of liquid expelled from the syringe from the recorded differential pressure over time.