Background: In the era of BPJS, RsML especially in class III wards experienced a lot of surge in patients, especially in class III wards. Research purposes: to find out the unit cost of accommodation in class III inpatient wards based on the ABC method of the system and to distinguish the results of traditional calculations that are still valid in RSML. Method: with qualitative research methods and case studies. The instrument used is financial documentation and accounting owned by the hospital. ABC Method (Activity Costing Costing System). Results: based on the calculation of unit costs Activity Based Costing method (ABC) calculation of unit cost of accommodation for class III ward of Rp 110,401, while the cost of inpatient fees that apply in RsML for class bengsal III is Rp 125,000. Conclusion: The results of this study show the difference, that with ABC the system produces a smaller calculation than the traditional system that applies in RsML. Keywords: Activity Based Costing Method