The expected date of delivery is of paramount importance to pregnant woman, her relatives, and treating doctor. It is useful for arranging help required and to take appropriate obstetric decisions. This study was aimed to find more accurate method to know Expected date of delivery. This was prospective study done on 800 new cases coming to Antenatal Outpatient clinic. A total of 318 cases were included in analysis. Rest of them were excluded for various reasons. In the patients selected Expected date was calculated according to Naegle's rule calculation (L.M.P. date +280days) and by measuring femur length and biparietal diameter of fetal head measured on ultrasound scan and using Hadlock charts already available on ultrasound machines. Actual date when these patients went in labour spontaneously was noted eventually. Accuracy rates for ultrasound scan and menstrual period estimates of date of delivery were calculated as the percentage estimates accurate to within a given number of days. Significance tests and confidence intervals for differences in these paired rates were calculated.The cases where the estimated dates of delivery disagree are termed discrepant. For 33 patients the estimated dates of delivery from the two methods were identical and in 27 of these cases they were exactly correct. The percentages of the 285 discrepant cases in which the scan gave closer prediction of the date of delivery than the last menstrual period.It can be concluded that all persons involved with antenatal care, may be doctors or the patients and relatives should rely the estimated date of delivery derived from ultrasound scan and ignore the one calculated by Naegle's rule once the satisfactory scan has been obtained.The study was undertaken to compare and know the more accurate and reliable method to calculate Expected Date of Delivery for the pregnant women coming to Antenatal Outpatient department. Total 800 women were included in the study initially coming from different parts of the district. Out of the above only 318 women were taken for analysis and the rest were excluded for various reasons.