The life-cycle of the K-1 tank has been 10 years simply applying that of the U.S. M-1 tank. Therefore, this paper is focused on determination of an economic life-cycle for the K-1 tanks. The current operation cost is adjusted by interest rate and the depreciation cost is applied in this study for more reliable estimation of the life-cycle cost. The Equivalent Annual Method is utilized and then various regression techniques are applied for deriving an effective economic life-cycle. The economic life-cycle of the K-1 tank results in 13 years in this study. considering 95% confidence interval, the life cycle of the K-1 tank is between 10.5 years and 15.5 years.