The design of a phase-shift interferometer in the extreme ultraviolet (EUV) is described. The interferometer is expected to achieve a significantly higher precision as compared with similar instruments that utilize lasers in the visible range. The interferometer's design is specifically adapted for its utilization with a table top pulsed capillary discharge EUV laser. The numerical model evaluates the errors in the interferograms and in the retrieved wavefront induced by the shot-to-shot fluctuations and pointing instabilities of the laser.