Background Leprosy occurs due to primary M. leprae infection that attacks the peripheral nerves. Limited resources directly links the bacterial index (BI) with the grade of disability in leprosy patients in Indonesia, even though the problem of disability greatly affects quality of life of patients. Methods A cross-sectional retrospective study approach was conducted. Total sampling technique was performed from medical records of patients with diagnosis of PB or MB leprosy, accompanied by grade 0, 1 or 2 disability. Correlation analysis test was performed to determine the correlation between BI and grade of disability in leprosy patients. Results A total of 278 patients were included in this study, divided into 13 patients (4.7%) of PB leprosy and 265 patients (95.3%) of MB leprosy. Significant results were obtained in 5 out of 9 groups: (a) hand group in PB+MB leprosy (p value: 0.047); (b) foot group in PB+MB leprosy (p value: 0.002); (c) foot group in PB leprosy (p value: 0.000); (d) hand group in MB leprosy (p value: 0.021); and (e) foot group in MB leprosy (p value: 0.006). Conclusion Positive correlations between BI and grade of disability were found in 56% of the analysis groups. [ABSTRACT FROM AUTHOR]