Inter-run calibration is used where qPCR samples are split over several runs conducted within the same experiment due to limited capacity of one run. We however encourage researchers to avoid this set up as it can easily invoke bias in the comparison. Where capacity of a single run is exceeded reactions should be preferentially split such that different genes are analysed on different plates. Note that the inter-run calibration shall be done for each gene specific. There may be more than one calibration sample used for one and the same gene and each calibration sample may be split over more than one PCR reactions, for instance, to cover a larger range of Ct values. In the process of calibration every calibrator PCR reaction(s) will be matched with calibrator reaction(s) on another plates containing the same gene analysed. Eventually, runs will be calibrated according to one calibrator run determined by user.