In a method for determining the volume of liquid, such as fuel, being dispensed from a liquid pump unit, a correction of the number of pulses generated by a pulse generator corresponding to the volume flow rate when dispensing liquid is carried out. The purposes of the correction is to produce a predetermined number of pulses per unit of volume of the liquid. The correction preferably comprises disregarding a pulse for ever Nth produced pulse or adding a pulse in addition to the pulses generated for ever Nth generated pulse. This correction, which can be made continuously during volume determination and which does not require any multiplications, is preferably realized by a processor unit and its associated software in an apparatus for volume determination.A method for carrying out calibration for determining N is also disclosed.