The paper presents the methodology of testing common rail fuel injectors, which consisted in extending the standard diagnostic proce-dures with the analysis of the resulting fuel delivery fields. The calculations were carried out in a popular spreadsheet, using Gauss's formulas (the so-called shoelace formula). In this way, the necessity to modify the test bench software was eliminated, as the analytical process took place after the end of the active experiment phase. It has been shown that the proposed solution should be particularly useful in problematic situations where clear-cut verification and assessment of the technical condition of the fuel injectors is sometimes difficult, as shown in the example. In addition, implementation in a digital environment allows the presented algorithms to be reused in research with a similar profile.