A method for operating a wind turbine for generating electrical power from wind, wherein - the wind turbine has an aerodynamic rotor with a rotor hub and rotor blades of which the blade angle (α) is adjustable, and the aerodynamic rotor can be operated at a variable rotation speed, and - the wind turbine has a generator, which is coupled to the aerodynamic rotor, for the purpose of generating a generator power, wherein - the generator can be operated with a variable generator torque, comprising the steps of: - determining a loading variable on the wind turbine , which indicates a load on the wind turbine due to the wind, - changing to a loading mode when the loading variable reaches or exceeds a loading limit value, and - reducing the rotation speed and/or the generator power in a loading mode, wherein the method is charactereized by the steps of - detecting the measured values of strain gauges , which are arranged at all blade roots (211-213) of the rotor blades, as vectorial force variables (F1-F3), - calculating a vectorial hub bending moment component (M B1 ,M B2 ,M B3 ) for each rotor blade, - vectorial summation of the vectorial hub bending moment components (M B1 ,M B2 ,M B3 ) to form a common hub bending moment (M B ) to form the loading variable. - the wind turbine has an aerodynamic rotor with a rotor hub and rotor blades of which the blade angle (α) is adjustable, and the aerodynamic rotor can be operated at a variable rotation speed, and - the wind turbine has a generator, which is coupled to the aerodynamic rotor, for the purpose of generating a generator power, wherein - the generator can be operated with a variable generator torque, comprising the steps of: - determining a loading variable on the wind turbine , which indicates a load on the wind turbine due to the wind, - changing to a loading mode when the loading variable reaches or exceeds a loading limit value, and - reducing the rotation speed and/or the generator power in a loading mode, wherein the method is charactereized by the steps of - detecting the measured values of strain gauges , which are arranged at all blade roots (211-213) of the rotor blades, as vectorial force variables (F1-F3), - calculating a vectorial hub bending moment component (M B1 ,M B2 ,M B3 ) for each rotor blade, - vectorial summation of the vectorial hub bending moment components (M B1 ,M B2 ,M B3 ) to form a common hub bending moment (M B ) to form the loading variable. - determining a loading variable on the wind turbine , which indicates a load on the wind turbine due to the wind, - changing to a loading mode when the loading variable reaches or exceeds a loading limit value, and - reducing the rotation speed and/or the generator power in a loading mode, wherein the method is charactereized by the steps of - detecting the measured values of strain gauges , which are arranged at all blade roots (211-213) of the rotor blades, as vectorial force variables (F1-F3), - calculating a vectorial hub bending moment component (M B1 ,M B2 ,M B3 ) for each rotor blade, - vectorial summation of the vectorial hub bending moment components (M B1 ,M B2 ,M B3 ) to form a common hub bending moment (M B ) to form the loading variable. <EOS>