A method for obtaining exposure data may be provided. MTO (Mask Tape Out) design data for a mask pattern may be received. A mask data preparation operation with respect to the MTO design data may be performed to obtain exposure data. Two-dimensional contours of a plurality of types of test patterns in an exposure mask may be extracted through simulation using a mask process model. First critical dimensions may be measured at measurement points of the contour of each of the plurality of types of test patterns by using a metrology algorithm. The first critical dimensions may be averaged to obtain a first average critical dimension for each of the plurality of types of test patterns. Second critical dimensions in consideration of dispersion in each of the plurality of types of test patterns may be measured using an inverse function of a standard normal distribution, and the second critical dimensions may be averaged to obtain a second average critical dimension for each of the plurality of types of test patterns. A mean to target (MTT) value may be calculated as a difference between the second average critical dimension and a target critical dimension for each of the plurality of types of test patterns. Differences between ones of the MTT values may be calculated. When one or more of the differences between the ones of the MTT values may is outside of a tolerance threshold, the exposure data may be corrected.