A method for electromagnetic and real-time measurement of a percentage of austenite contained in a steel strip in continuous motion during in-line manufacture or transformation thereof, by a device including the steel strip and a measuring device including at least: an alternating-current generator; a first coil supplied by the alternating-current generator, called a transmitting coil, and a second coil, called a receiving coil, the first and second coils being arranged parallel to each other or coaxial and on both sides of the steel strip, a distance between the coils being fixed and between 10 and 200 mm; a core of ferromagnetic material being a center of each coil, respectively; and at least one voltage-measuring device connected to terminals of the receiving coil, being a multimeter or an electronic acquisition system having an analog-digital converter coupled to a computer, to obtain the percentage of austenite contained in the steel strip.