Background: Dengue infection is a disease that progresses rapidly to life-threatening conditions. Our goal was to develop a practical scoring system based on clinical profiles and routine tests to predict the severity of infection. Methods: This cross-sectional observational study included 500 patients with dengue infection. Patient demographics, clinical symptoms, regular laboratory tests, and results were collected. Dengue infections are divided into three classes, depending on their severity: dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS). Based on the total score, patients were divided into three severities. Results: Patients with DSS and DHF scored higher with worsening clinical features and routine laboratory tests compared to DF. Clinical predictors of severity include older age, increased white blood cell (WBC) count, increased hematocrit, increased prothrombin time, decreased platelet count, decreased blood pressure, presence of peri-gallbladder (GB) edema, third space loss, hepatomegaly, and other organ involvement. The severity range is 0–12, and the score is 0–3 for DF, 4–8 for DHF, and 9–12 for DSS. Based on the derived scores, patients were classified according to their original severity in 63% of cases. Conclusion: This dengue infection severity scores correctly classified patients according to their original severity grade of DF, DHF, or DSS. This scoring system helps to quickly assess dengue infections and start treatment according to the correct severity category.