An overlay metrology system includes a controller to receive, from an overlay metrology tool, overlay measurements on multiple sets of overlay targets on a sample with a range of values of a measurement parameter, where a particular set of overlay targets includes overlay targets having one of two or more overlay target designs. The controller may further determine scaling metric values for at least some of the overlay targets, where the scaling metric for a particular overlay target is based on a standard deviation of the overlay measurements of the corresponding set of overlay targets. The controller may further determine a variability of the scaling metric values for each of the two or more sets of overlay targets. The controller may further select, as an output overlay target design, one of the two or more overlay target designs having a smallest scaling metric variability.