This study intends to review the operational estimation skills of pre-service primary school teachers, and to see if they are able to use the correct strategy when making estimates. For this purpose, the "estimation skills test" comprised of 41 questions allowing estimates using 14 distinct estimation strategies was used. 209 pre-service primary school teachers took part in the study. The responses provided by the pre-service teachers were scored on the basis of the accuracy of the estimation. Furthermore, the responses to the questions in the test were scored with reference to the applicability of the estimation method, on a binary scale of 0 and 1. The study revealed that the pre-service primary school teachers had mediocre operational estimation skills, and that majority of them failed to use the optimal strategy. In this context, one should recommend the offering of undergraduate courses to pre-service primary school teachers to improve their estimation skills.