Background: during stimulation, estradiol levels represent the dynamic hormonal interaction of follicle development. Some studies have been done to evaluate the influence of day-hCG estradiol assay and IVF outcome. However, this assay does not reflect the total exposure of estradiol throughout stimulation. Hence the concept of calculating the area under the curve (AUC) of estradiol during ovarian stimulation is thought to be a better parameter to evaluate total exposure of estradiol to the entire process of IVF. Methods: a retrospective analysis of data from a fertility center in a tertiary hospital. Between 2011-2016, there were long GnRH agonist cycles and short GnRH antagonist cycles eligible for analysis. Data including subject’s characteristics, the level of estradiol on day-2, day-6, and day-hCG during controlled ovarian stimulation were obtained. Those data were plotted, and area under the curve of each subject was calculated. Statistical analysis was done using student t-test while p < 0.05 was considered significant. Results: there were no significant differences in subject’s age (33.4 vs. 34.2 years, p = 0.12), day-3 of menstrual cycle FSH level (7.1 vs. 7.3 mIU/mL, p = 0.64), and day-3 estradiol level (35.1 vs. 36.5 pg/mL, p = 0.61). The estradiol level on day-5 of COS was 324.9 (273.1) pg/mL and 363.3 (293) pg/mL (p = 0.36), and at the day of hCG administration was 2461.8 (2283.7) ng/mL and 2558.2 (2043) ng/mL (p = 0.76). Estradiol area under the curve for long protocol and short protocol was 9205.2 (7683.7) pg/mL and 9732.9 (6893.9) pg/mL respectively (p = 0.63). Conclusion: our results indicate that there are no significant differences in the area under the curve of estradiol between two protocols.