The method electromagnetically measures a 
pipe inner 
diameter ID and a 
pipe ratio of magnetic permeability to electrical 
conductivity μ2 / σ2 by means of a measuring arrangement 1 comprising a 
transmitter coil 2 and a 
receiver coil 3, both coils being coaxial to and longitudinally spaced from each other, the measuring arrangement 1 being adapted to be positioned into the 
pipe CS and displaced through the pipe. The method comprises the steps of:a1) exciting the 
transmitter coil 2 by means of a 
transmitter current Ii, the transmitter current having a first excitation frequency f1,a2) measuring a 
receiver voltage Vi at the 
receiver coil 3, a3) determining a transimpedance Vi / Ii between the 
transmitter coil 2 and the 
receiver coil 3 based on the transmitter current Ii and the receiver 
voltage Vi, and determining a measurement ratio Mi based on said transimpedance,b) repeating the excitation step a1), the measuring step a2), the transimpedance and the measurement ratio determination step a3) for at least a second excitation frequency f2 so as to define a measurement ratio vector [M1, M2, . . . Mn],c) calculating a prediction function vector [G1, G2, . . . Gn] based on the first and at least the second excitation frequency, a plurality of potential pipe ratio of magnetic permeability to electrical 
conductivity and a plurality of potential pipe inner 
diameter ID, andd) applying a minimizing 
algorithm onto the measurement ratio vector [M1, M2, . . . Mn] and the prediction function vector [G1, G2, . . . Gn] and determining the pipe inner 
diameter and the pipe ratio of magnetic permeability to electrical 
conductivity corresponding to a maximum solution of the 
algorithm.