A method for use in planning metrology measurements, the method comprising: providing inverse total measurement uncertainty (TMU) analysis equations for upper and lower confidence limits TMUUL and TMULL of the TMU being independent on prior knowledge of measurements by a tool under test (TuT) and a reference measurement system (RMS), thereby enabling estimation of input parameters for said equations prior to conducting an experiment of the TMU analysis; and determining at least one of a total number N of samples to be measured in the TMU analysis and an average number ns of measurements per sample by the RMS.