Precise estimation of reference evapotranspiration (ET_o) is fundamental for irrigation management, as well as sustainable water use in agriculture. Nevertheless, using the FAO-56 Penman-Monteith method to calculate ETO is frequently limited due to the lack of sufficient climate data. The present study aims to determine the method that requires the least data and is best suited for calculating reference evapotranspiration in the Tahla plateau by comparing eight empirical formulas with the FAO-56 Pеnman–Mоnteith Mеthоd. The performance of the tested methods was assessed using the Root Mean Square Error (RMSE), Mean Bias Error (MBE), Mean Absolute Percentage Error (MAPE), coefficient of determination (R²), Willmott’s index of agreement (d), and Nash-Sutcliffe efficiency (NSE). The results obtained show shows that Turc method way is the best (RMSE= 0.38 mm/day, NSE= 0.95). Thornthwaite and Hargreaves-Samani were ranked second with very close performances, both methods having the same scores on the two indices (d= 0.95, NSE= 0.77) and close RMSE values (0.79 and 0.80 mm/day), respectively. Thornthwaite slightly outperforms Hargreaves-Samani in terms of error and bias, while Hargreaves-Samani is characterized by a stronger correlation (R² = 0.99 vs 0.89) and a more regular error throughout the year, which can be easily corrected by local calibration. On the other hand, the Blaney-Criddle, Blaney-Criddle modified by Shih et al., (1977), Ivanove, Jensen-Haise and Eagleman methods are not well calibrated to Penman-Monteith ETo in the Thala plateau. The findings of this study help improve water management in agriculture and support durable irrigation strategies.