A method of operating a laundry treatment machine, the laundry treatment machine being configured to process laundry via rotation of a tub, the method comprising: aligning a rotor of a motor during a motor alignment section (Ta), wherein the motor alignment section (Ta) includes a first section in which a first current flows through the motor and a second section in which a second current flows through the motor; accelerating a rotation velocity of the tub during an accelerated rotating section (Tb); rotating the tub at a constant velocity during a constant velocity rotating section (Tc); calculating tolerance (ΔV) between a voltage command value during the first section and a voltage command value during the second section in the motor alignment section (Ta); calculating a back electromotive force (emf) during the constant velocity rotating section (Tc) based on a voltage command value and the current command value for the constant velocity rotating section (Tc) and the equivalent resistance value (Rs) of the motor; calculating an average back electromotive force value (emf_ATC) based on the back electromotive force (emf) and a discrete value corresponding to a length of a partial section of the constant velocity rotating section (Tc); calculating a back electromotive force compensation value (emf_com) based on the average back electromotive force value (emf_ATC) and the tolerance (ΔV); and calculating an amount of laundry in the tub based on a difference between an average current command value to rotate the motor during the accelerated rotating section (Tb) and an average current command value to rotate the motor during the constant velocity rotating section (Tc) and the back electromotive force compensation value (emf_com). aligning a rotor of a motor during a motor alignment section (Ta), wherein the motor alignment section (Ta) includes a first section in which a first current flows through the motor and a second section in which a second current flows through the motor; accelerating a rotation velocity of the tub during an accelerated rotating section (Tb); rotating the tub at a constant velocity during a constant velocity rotating section (Tc); calculating tolerance (ΔV) between a voltage command value during the first section and a voltage command value during the second section in the motor alignment section (Ta); calculating a back electromotive force (emf) during the constant velocity rotating section (Tc) based on a voltage command value and the current command value for the constant velocity rotating section (Tc) and the equivalent resistance value (Rs) of the motor; calculating an average back electromotive force value (emf_ATC) based on the back electromotive force (emf) and a discrete value corresponding to a length of a partial section of the constant velocity rotating section (Tc); calculating a back electromotive force compensation value (emf_com) based on the average back electromotive force value (emf_ATC) and the tolerance (ΔV); and calculating an amount of laundry in the tub based on a difference between an average current command value to rotate the motor during the accelerated rotating section (Tb) and an average current command value to rotate the motor during the constant velocity rotating section (Tc) and the back electromotive force compensation value (emf_com).