Abstract Background Estimation of gestational age plays a pivotal role in day to day clinical practice for appropriate management of newborn. The trans-cerebellar diameter can predict gestational age in cases of variations of fetal head shape such as dolichocephaly and brachycephaly or even when fetus is in posterior position. Trans-cerebellar diameter (TCD) may be useful in gestational age estimation. Aim and methodology To determine the accuracy of trans-cerebellar diameter in the estimation of gestational age of fetus and comparing the conventional parameters like head circumference, biparietal diameter, abdominal circumference and femur length in the measurement of gestational age. This is a prospective, cross-sectional analytical study done in the Radiology Department in those patients who were referred to the department for a routine antenatal ultra-sonogram checkup. Results Comparison of trans-cerebellar diameter with gestational age derived from last menstrual period indicates that there is a linear relationship throughout the gestational ages. There is a strong correlation of trans-cerebellar diameter with other conventional parameters namely biparietal diameter, femur length and abdominal circumference of which Femur length correlates well with the trans-cerebellar diameter. Correlation of transcerebellar diameter with gestational age shows a R2 of 0.995 (p value < 0.001). Conclusion Trans-cerebellar diameter is best in estimation of gestational age when compared to biparietal diameter, femur length and abdominal circumference. The regression formula derived from trans-cerebellar diameter measurement can be applied to determine the gestational age of fetus.