A stand alone ice making appliance or an ice maker within an appliance is provided including a water inlet, a water inlet valve disposed within the water inlet configured to allow water passage when in an open position and configured to prevent water passage when in a closed position, a reservoir in fluid communication with the water inlet, a water level sensor disposed in the reservoir, and a control unit in electrical communication with the water level sensor and the water inlet valve. The control unit is configured to calculate a fluid flow rate using the time between the water inlet valve opening and the water level sensor communicating when a first predetermined water level has been reached within the reservoir, and use the calculated flow rate to calculate a total water inlet valve open time to fill the reservoir to a second predetermined water level.