An apparatus and method for precisely dispensing liquid fluid from a container are disclosed. The apparatus comprises a metering unit having a gas feedthrough channel with a first end extending in a gas containing part of the chamber and a second end opposite the first end extending outside the chamber, the metering unit further comprising a flow sensing assembly configured to measure a gas pressure differential Δp and/or gas flow V{dot over ( )} within the gas feedthrough channel and to introduce or release a determined volume of gas in the chamber to dispense a controlled volume of liquid from the chamber.