Enter climate data to calculate reference evapotranspiration using the FAO Penman-Monteith method. This calculator provides accurate estimates of crop water requirements for agricultural planning and irrigation management.
Note: For more accurate results, you can import weather data from an EPW file using our EPW Import Tool.
Saturation Vapor Pressure (es): -- kPa
Actual Vapor Pressure (ea): -- kPa
Slope of Vapour Pressure Curve (Δ): -- kPa °C⁻¹
Psychrometric Constant (γ): -- kPa °C⁻¹
Net Radiation (Rn): -- MJ m⁻² d⁻¹