The present invention relates to a method and a device for calibrating a fuel metering system having at least one injector in an internal combustion engine, in particular of a motor vehicle, wherein there is at least one preliminary injection temporally prior to a main injection and an injector to be calibrated is subjected to at least two test injections temporally prior to the at least one preliminary injection; the first test injection is performed with a first actuation duration during which the injector does not yet open and the at least second test injection is performed in a subsequent injection cycle with a respective incrementally increased actuation duration relative to the first test injection, until a change of an operating parameter of the fuel metering system or the internal combustion engine occurs; a minimum actuation duration for the injector is determined from the actuation duration present at said change of the operating parameter.