A variable orifice flow meter system includes a housing defining a flow passage and at least one plate extending into the flow passage and defining an orifice. The at least one plate is movably supported such that a size of the orifice may be adjusted. Upstream and downstream pressure sensors may measure fluid pressures upstream and downstream of the orifice and a drive mechanism may move the at least one plate. A controller may instruct the drive mechanism to move the at least one the plate such that a predetermined orifice size is defined in response to detecting an upstream pressure within a predetermined pressure range, determine a pressure differential across the orifice and calculate a flow rate through the flow passage based on the pressure differential when the pressure differential meets a predetermined threshold.