Doctor Scientiae - DSc / Determining arch perimeter is of importance in both a clinical setting, where it is used to determine space requirements, as well as in an epidemiological setting where it is used to describe large populations. Physical measurement of arch perimeter is time consuming and may be prone to operator errors when done on study casts and even more so in a clinical situation. The use of a simple mathematical model to predict arch perimeter, using a few measurements that can be done easily and reliably, would be of great use to the practitioner.