When measuring $$$T_1, T_2, T_2^*, PD$$$, or $$$B_1^+$$$, we prefer the MRI sequence that provides the best precision in the allowed scan time (i.e. having optimal time efficiency). However, experimentally determining the time efficiency is impractical when comparing many sequences, each possibly with varying settings, and multiple tissue types of interest. Here, we derive time efficiency through Bloch simulations which is applicable to any MRI sequence and tissue type. A specific strength of our framework is that it does not require an explicit fitting procedure which may not yet exist when designing novel MR sequences.