Crown-rump length, hind-foot length and weight of known-age coyote (Canis latrans) fetuses dated from estrus and metestrus onset were measured both fresh and after formalin fixation. Regression equations were established for predicting fetal age. All equations provide reliable estimates of age; the lowest correlation coefficient among the 12 sets of data was 0.97. Crown-rump measurements provided the best estimate of fetal age. To facilitate estimating breeding dates from field-collected specimens, a ruler-type scale was derived from the crown-rump measurements of fresh, estrus-dated fetuses.