A method for determining the actual offset value of an injector (5) of an internal combustion engine (1); the method includes the steps of: determining, at a stationary rate, a target injection time (T inj ) for the injector (5); driving the injector (5) to perform a single injection having a duration equal to the target injection time (T inj ); subsequently driving the injector (5) to perform n subsequent sub-injections, each having a duration equal to one n-th of the target injection (T inj ); measuring the exhaust gas titre (λ 1 ) by performing the single injection; measuring the exhaust gas titre (λ 2 ) by performing the n sub-injections; and determining the actual offset value (T offset ) of the injector (5) according to the variation of the exhaust gas titre by performing the single injection and by performing the n sub-injections.