A method for determining an amount of nucleic acid molecule copies of a preselected nucleic acid molecule in a sample, comprising the steps of a) generating fragments of the preselected nucleic acid molecule, b) providing the amount of fragments for said preselected nucleic acid molecule, c) providing a distribution of fragment coverage over a genetic coordinate for said preselected nucleic acid molecule, d1) generating a plurality of virtual fragments based on the genetic coordinates of the preselected nucleic acid molecule, so that the generated virtual fragments have substantially the distribution of fragment coverage over the genetic coordinate according to step c), or d2) determining the nucleic acid sequence of fragments obtained in step a) and providing each nucleic acid sequence of a fragment as virtual fragment; thereby obtaining a plurality of virtual fragments, e) assembling the obtained virtual fragments from step d) into fragment sequences, wherein each virtual fragment is assembled into a fragment sequence which is composed of matching virtual fragments, until all virtual fragments of step d) have been either assembled into a fragment sequence or do not match with any other non-assembled virtual fragment or fragment sequence and all fragment sequences do not match with any other fragment sequence, wherein each final fragment sequence and non-assembled virtual fragment is regarded as a virtual copy, f) obtaining the amount of virtual fragments from step d) per virtual copy obtained in step e), g) whereby the amount of the copies of a preselected nucleic acid molecule in a sample can be calculated from the fragment amount of step b) and the amount of annealed fragments per virtual copy of step f). a) generating fragments of the preselected nucleic acid molecule, b) providing the amount of fragments for said preselected nucleic acid molecule, c) providing a distribution of fragment coverage over a genetic coordinate for said preselected nucleic acid molecule, d1) generating a plurality of virtual fragments based on the genetic coordinates of the preselected nucleic acid molecule, so that the generated virtual fragments have substantially the distribution of fragment coverage over the genetic coordinate according to step c), or d2) determining the nucleic acid sequence of fragments obtained in step a) and providing each nucleic acid sequence of a fragment as virtual fragment; thereby obtaining a plurality of virtual fragments, e) assembling the obtained virtual fragments from step d) into fragment sequences, wherein each virtual fragment is assembled into a fragment sequence which is composed of matching virtual fragments, until all virtual fragments of step d) have been either assembled into a fragment sequence or do not match with any other non-assembled virtual fragment or fragment sequence and all fragment sequences do not match with any other fragment sequence, wherein each final fragment sequence and non-assembled virtual fragment is regarded as a virtual copy, f) obtaining the amount of virtual fragments from step d) per virtual copy obtained in step e), g) whereby the amount of the copies of a preselected nucleic acid molecule in a sample can be calculated from the fragment amount of step b) and the amount of annealed fragments per virtual copy of step f).