Abstract: A system for determining an actual measurement of a structure on a sample using a measurement tool with a calibration standard having measurement sites. A previously measured site on the calibration standard with a first known metric is measured with the measurement tool to produce a first measurement. A newly measured site on the calibration standard, also with a second known metric is measured with the measurement tool to produce a second measurement. A calibration factor for the measurement tool is computed by comparing the first measurement to the first known metric and the second measurement to the second known metric. The structure on the sample is then measured using the measurement tool to produce a precursor measurement. This precursor measurement is adjusted with the calibration factor to produce an intermediate measurement. Then the intermediate measurement is adjusted with the sample composition data to produce the actual measurement.