Embodiments of the disclosure can relate to quantification of gas turbine inlet filter blockage. In one embodiment, a method can include receiving data associated with an inlet flow conditioning system associated with a turbine in a power plant. The method may further include determining an inlet flow associated with the turbine, based at least in part on operational data from the turbine. The method may further include determining an effective area of the inlet flow conditioning system, based at least in part on the inlet flow associated with the turbine. The method can further include determining a fouling rate of the inlet flow conditioning system, based at least in part on a difference between the effective area of the inlet flow conditioning system and a corresponding effective area of the inlet flow conditioning system determined at a prior operation. The method may further include identifying a corrective recommendation for the inlet flow conditioning system, based at least in part on the fouling rate and a performance target of the turbine.