Method and system in connection with a motor operated tension measuring roll (1) for compensating an error in tension measuring of a continuous material web, the method comprising defining the tension Tmeas of a material web (4) by a force sensor (3) provided at the tension measuring roll. The method comprises defining the frictional couple Tμ and moment of inertia J of the tension measuring roll before tension measuring during operation, defining a torque Tmot generated by the driving motor of the tension measuring roll during operation, defining a torque Twm directed to the material web by the tension measuring roll by subtracting the frictional couple Tμ and moment of inertia J from the defined torque Tmot generated by the driving motor, defining a force FT directed to the material web on the basis of the torque Twm directed to the material web by the tension measuring roll, defining, on the basis of the force FT directed to the material web, a component of force FTm of the measuring sensor in the measuring direction directed to the material web by the tension measuring roll, and subtracting from the tension Tmeas defined by the force sensor the component of force FTm of the measuring sensor in the measuring direction directed to the material web by the tension measuring roll to provide a corrected measuring signal.