Method for evaluating a biomass in a dielectric medium to be measured, in particular cells in suspension in a fluid, in which the capacitance and conductance measurements are carried out using an apparatus comprising electrodes in contact with the medium and electronic means for processing the capacitance and conductance signals obtained from said electrodes, this capacitance signal being contaminated with capacitance errors due to random polarization, capacitance errors due to systematic polarization, and capacitance errors due to the overall errors originating from the electronic means, - wherein the capacitance errors due to random polarization are corrected separately from those due to systematic polarization and those due to the electronics, - wherein the method also comprises (i) global modelling of the systematic polarization and of the capacitance errors due to the overall errors of the electronics, in the form of a common equation of the model of capacitance errors (C cal (G, f)), a function of the conductance of the medium and the excitation frequency (f) of the conductive electrodes, and (ii) determination of corrected capacitance values (Cm_corr(G, f)) by comparing each raw capacitance measurement (Cm(G, f)) originating from the apparatus and carried out at a predetermined frequency (f), to the value of said common equation of the model of capacitance errors (C cal (G, f)) at said predetermined frequency (f), - wherein the evaluation of the biomass is obtained from a difference (ΔC X (G,f 2)) between a first capacitance signal of said medium (C X_FG_C (G,f 2)) obtained on the basis of a first measurement of the raw capacitance (Cm_(G, f 2)) of said medium measured at a first frequency (f 2) and a second corrected capacitance signal (Cm_cor(G, f 3)) obtained on the basis of a second measurement of the raw capacitance (Cm_(G, f 3)) of said medium measured at a second frequency (f 3), the method comprising a separate correction of each of the raw capacitance signals (Cm_(G, f 2), (Cm_(G, f 3)) according to at least a first level of correction, this first level of correction comprising a correction of said raw capacitance signals according to said model of capacitance error (C cal (G, f)) dependent on the conductance of said medium at said first and second frequencies, so that corrected first and second capacitance signals (Cm_cor(G,f 2), (Cm_cor(G,f 3)) are obtained respectively. - wherein the capacitance errors due to random polarization are corrected separately from those due to systematic polarization and those due to the electronics, - wherein the method also comprises (i) global modelling of the systematic polarization and of the capacitance errors due to the overall errors of the electronics, in the form of a common equation of the model of capacitance errors (C cal (G, f)), a function of the conductance of the medium and the excitation frequency (f) of the conductive electrodes, and (ii) determination of corrected capacitance values (Cm_corr(G, f)) by comparing each raw capacitance measurement (Cm(G, f)) originating from the apparatus and carried out at a predetermined frequency (f), to the value of said common equation of the model of capacitance errors (C cal (G, f)) at said predetermined frequency (f), - wherein the evaluation of the biomass is obtained from a difference (ΔC X (G,f 2)) between a first capacitance signal of said medium (C X_FG_C (G,f 2)) obtained on the basis of a first measurement of the raw capacitance (Cm_(G, f 2)) of said medium measured at a first frequency (f 2) and a second corrected capacitance signal (Cm_cor(G, f 3)) obtained on the basis of a second measurement of the raw capacitance (Cm_(G, f 3)) of said medium measured at a second frequency (f 3),