A method of measuring a critical dimension may include forming an object pattern on a substrate and forming a plurality of reference patterns on the substrate, wherein each of the plurality of reference patterns has a different critical dimension. An optical property of each of the plurality of reference patterns may be measured to provide a respective measured optical property for each of the reference patterns, and an optical property of the object pattern may be measured to provide a measured optical property of the object pattern. The measured optical property of the object pattern may be compared with the measured optical properties of the reference patterns, and a critical dimension of the object pattern may be determined as being the same as the critical dimension of the reference pattern having the measured optical property that is closest to the measured optical property of the object pattern. Related devices are also discussed.