CT-Scan abdomen is an examination to see the anatomy and pathology of the abdominal organs, and the scanning image results are in the form of three-dimensional axial images of the body. The radiation dose released from the CT-Scan examination is more significant than other radiology modalities. Therefore, it is very important to estimate the patient's dose accurately. Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) are dose parameters used in CT-Scan to describe the dose value received by the patient. However, these parameters are the output of the CT-Scan, not as the dose received by the patient. The Size Specific Dose Estimate (SSDE) method based on AAPM Report No. 204 is used to determine the estimated dose received by the CT-Scan Abdomen patient. Calculations are done manually and with IndoseCT software. The data used are secondary data of 60 patients, namely 21 females and 39 males, who were on the CT-Scan Abdomen examination without contrast from the Instalasi Radiologi Rumah Sakit Semen Gresik. The SSDE value is obtained from the multiplication between the conversion factor and CTDIvol, where the conversion factor is an effective diameter function. The analysis examined the error value in manual calculations and IndoseCT software in men and women, the relationship between effective diameter and scanning radiation output (CTDIvol), and dose estimation estimates (SSDE). The difference in SSDE values between manual calculations and IndoseCT software was insignificant. The highest error value in women was 3% and 3.2% in men. Meanwhile, the relationship between effective diameter (Deff) and scanning radiation output (CTDIvol) and dose estimation estimates (SSDE) showed that the correlation between effective diameter (Deff) and CTDIvol showed a stronger correlation, namely with R2 around 0.7 in women and men, compared to the correlation between effective diameter (Deff) and SSDE with R2 around 0.03 in women and 0.2 in men. Keywords: CT-Scan, Abdomen, Size Specific Dose Estimate (SSDE).