Method for calibrating at least one non-selective chemical sensor, referred to as "sensor to be calibrated ", by means of at least one reference sensor (2, 2'), said sensor to be calibrated and said reference sensor (2, 2') being in contact with a same chemical medium (4, 4'), said sensor to be calibrated being configured to determine a chemical signal of the quantity of a group of chemical compounds in said chemical medium (4, 4'), said reference sensor (2, 2') being configured to determine a reference signal whose temporal variation is correlated with that of said chemical signal, said sensor to be calibrated comprising: - a measuring element of an electrical signal, which is a function of the quantity of said group of chemical compounds in said chemical medium (4, 4'), and - a calculation element of said chemical signal from a conversion function (f) specific to said sensor to be calibrated and configured to associate said measured electrical signal with the corresponding chemical signal according to the following relation: S1 = f, - said method being characterised by the fact that it comprises: - a step of measuring, during a reference period, a first chemical signal (S1 P1) by means of the sensor to be calibrated and a first reference signal (S2 P1) by means of the reference sensor (2, 2'), - a step of determining a first regression function (g P1) defined as follows: S2 P1 = g P1 (S1 P1), - at least one step of measuring, during a test period after the reference period, a second chemical signal (S1 P2) by means of the sensor to be calibrated and a second reference signal (S2 P2) by means of the reference sensor (2, 2'), - at least one step of determining a second regression function (g P2) defined as follows: S2 P2 = g P2 (S1 P2), - at least one step of calculating a difference (ε) between the first regression function (g P1) and the second regression function (g P2) and - when the difference (ε) is greater than a reference difference (ε ref), at least one step of determining an optimised conversion function (f*) so that the second regression function (g P2) is substantially equal to the first regression function (g P1), so as to calibrate the sensor to be calibrated. - a measuring element of an electrical signal, which is a function of the quantity of said group of chemical compounds in said chemical medium (4, 4'), and - a calculation element of said chemical signal from a conversion function (f) specific to said sensor to be calibrated and configured to associate said measured electrical signal with the corresponding chemical signal according to the following relation: S1 = f, - said method being characterised by the fact that it comprises: - a step of measuring, during a reference period, a first chemical signal (S1 P1) by means of the sensor to be calibrated and a first reference signal (S2 P1) by means of the reference sensor (2, 2'), - a step of determining a first regression function (g P1) defined as follows: S2 P1 = g P1 (S1 P1), - at least one step of measuring, during a test period after the reference period, a second chemical signal (S1 P2) by means of the sensor to be calibrated and a second reference signal (S2 P2) by means of the reference sensor (2, 2'), - at least one step of determining a second regression function (g P2) defined as follows: S2 P2 = g P2 (S1 P2), - at least one step of calculating a difference (ε) between the first regression function (g P1) and the second regression function (g P2) and - when the difference (ε) is greater than a reference difference (ε ref), at least one step of determining an optimised conversion function (f*) so that the second regression function (g P2) is substantially equal to the first regression function (g P1), so as to calibrate the sensor to be calibrated. - a step of measuring, during a reference period, a first chemical signal (S1 P1) by means of the sensor to be calibrated and a first reference signal (S2 P1) by means of the reference sensor (2, 2'), - a step of determining a first regression function (g P1) defined as follows: S2 P1 = g P1 (S1 P1), - at least one step of measuring, during a test period after the reference period, a second chemical signal (S1 P2) by means of the sensor to be calibrated and a second reference signal (S2 P2) by means of the reference sensor (2, 2'), - at least one step of determining a second regression function (g P2) defined as follows: S2 P2 = g P2 (S1 P2), - at least one step of calculating a difference (ε) between the first regression function (g P1) and the second regression function (g P2) and - when the difference (ε) is greater than a reference difference (ε ref), at least one step of determining an optimised conversion function (f*) so that the second regression function (g P2) is substantially equal to the first regression function (g P1), so as to calibrate the sensor to be calibrated.