Sanitary landfills pose a significant threat to the environment, primarily due to the presence of leachate. The characteristics of leachate and its detrimental impact on the surrounding ecosystem necessitate a comprehensive and rigorous approach to addressing this problem. Accurate estimation of leachate volume is crucial, and one essential factor for such calculations is evapotranspiration. To calculate evapotranspiration at the „Savina Stena“ sanitary landfill, the Thornthwaite method was employed using data sourced from the FAO AQUASTAT Climate Information Tool, spanning the period from 1990 to 2020. These values were then utilized to determine the average quantity of leachate generated at the landfill. The research findings reveal that the maximum daily amount of leachate recorded is 61.82 m³, with the highest levels occurring during winter months. Specifically, the leachate production for December was calculated at 61.82 m³/day, followed by January with 50.52 m³/day and February with 47.09 m³/day. Additionally, the study presents a comparison between the evapotranspiration values derived from the Thornthwaite method and those obtained from the FAO AQUASTAT Climate Information Tool over the same 31-year period. This comparison was performed by calculating the root mean square error (RMSE) and relative error (RE).