Converter was one tool unit that consisting 4 beds in the production process of sulfuric acid. The performance of this converter was supported by the addition of a vanadium pentaoxide (V2O5) catalyst. The process that occurring in the converter was double contacts – double absorbers. The purpose of this case was converter performance evaluation that using by SO2 conversion parameter to SO3. Primary data was the dry air flow rate that entering the burner, the SO2 gas content that be into the converter, the catalyst temperature of each converter bed, and the catalyst pressure in each bed converter. Data on the field showed that activity on bed I was 72,96%, and theoretical was 60%. Then, bed II gave 91,22%; 87%; on bed III was 96,85%; 94%; and bed IV was 99,9%; 99,73% as respectively. From these experiments could be concluded that result data was greater than the theoretical. The difference of this conversion indicated that the performance of the converter did not increase