The creep behavior of various materials is being increasingly studied using impression tests. However, the impression tests can provide data for the primary and secondary stages of the creep curve but not the third stage for the specimen doesn’t fail during the test. Creep studies without rupture data leaves the analysis incomplete. Hence there is a need to correlate the minimum velocity obtained from impression tests with rupture time to make the creep analysis complete. The present paper attempts to evaluate rupture time and Larson Miller parameter (LMP) from the impression test data of ZM21 Magnesium alloy. The rupture time (trup) was calculated from the steady state impression velocity using Monkman-Grant relationship (MGR) and the trup was used to calculate LMP. Impression tests were carried out between equivalent stresses of 180 MPa and 66.67 MPa and the temperature was varied between 448 K and 523 K. Larson-Miller constant of 10 was found to describe the LMP by logarithm of applied stress.