Extreme-ultraviolet (EUV) lithography remains a leading contender for use in the mass production of nanoelectronics at the 32\text{\hspace{0.17em} nm} node. Great progress has been made in all areas of EUV lithography, including the crucial issue of fabrication of diffraction-limited optics. To gain an accurate understanding of the projection optic wavefront error in a completed lithography tool requires lithography-based aberration measurements; however, making such measurements in EUV systems can be challenging. We describe the quantitative lithographic measurement of spherical aberration in a 0.3 numerical aperture. EUV microfield optic. The measurement method is based on use of the unique properties of a programmable coherence illuminator. The results show the optic to have 1\text{\hspace{0.17em} nm} rms spherical error, whereas interferometric measurements performed during the alignment of the optic indicated a spherical error of less than 0.1\text{\hspace{0.17em} nm \hspace{0.17em} rms} .