Cluster diameter analysis of the results of nanomaterial synthesis can be done using UV-Visible instruments with complex mathematical calculations. Another way is to use the Transform Electron Microscope (TEM) instrument directly. Both have advantages and disadvantages of each. This research compares the results of the two instruments on the results of nanogold and nanosilver synthesis. The results obtained diameter through calculations from UV-Visible nanogold spectra has a diameter of 20.62-20.68 nm, 20 ppm nanosilver has a diameter of 17.32 nm, while the combined nanogoldnanosilver has a diameter of 17.22-17.33 nm. The results of measuring the diameter of the cluster using the TEM instrument give more varied results. It was concluded that measurement of cluster diameter using UV-Visible gives a picture of the dominant cluster diameter that exists in colloidal nanomaterials both nanogold and nanosilver. The results of the measurement of the diameter of the clusters with the TEM instrument give a real picture of the variation of the diameter of the clusters produced by synthesis. Thus this study has the impact of making it easier for researchers to determine instrument choices as needed.