Extant literature on target-setting indicates that responding to achievability-related criticisms towards ex ante targets through repair actions are of significance in restoring fairness and maintaining the legitimacy of performance systems. By drawing on empirical materials on responses to unfairness criticisms raised against target-setting practices in a bank, the study shows that such legitimation work also requires responding to equity-related criticisms. Equity implies that, when situations differ, targets must be differentiated to make the intensity of efforts the same. This study shows that legitimately differentiating targets requires an original and highly complex commensuration work. This work is original because compared to prior commensuration studies it concerns the commensuration of efforts and not of entities. This work is complex because it is difficult to account for all differences during target-setting and because such differentiation can be made mechanically and discretionally, each form of differentiation bringing its own source of illegitimacy. Moreover, it is also complex because it is a distributed work, involving numerous actors with multiple concerns. Such commensuration work then appears to be continuous and dynamic. This complements prior studies in target-setting, which have focussed mainly on dyadic relations between a superior and a subordinate and on single-period adjustments to targets.