The aim of the present study was to buildup equation (s) for an intra-uterine fetal aging in Egyptian local sheep and she-goats breed using ultrasound. This study was carried out on a total number of 110 Baladi sheep and 74 she-goats under the field condition of Qalyubia governorate, Egypt. Ultrasound examination was conducted through trans-rectal and/or trans-abdominal routes. Throughout the gestation cycle between Day 26 and 112, Crown rump length (CRL) and biparietal diameter (BPD) were measured at least three times per test for each animal for accurate judgment. The correlation coefficient (R2) of BPD was higher than CRL in sheep and she-goats (0.9601 and 0.9598 vs. 0.898 and 0.903, respectively) at 39 to 112 days. Statistical analysis showed that no differences (P=0.258) between the BPD slopes represent ovine and caprine fetal growth rate. In conclusion, the use of ultrasound estimation in foetal biometry is useful to estimate the gestational age in sheep and she-goats with particular focus on BPD at all stages of pregnancy after breeding beyond Day 39.