Gain errors are corrected in an ADC chip including an integrator (17), a comparator (30), and a digital filter (37) by storing a gain-adjusted LSB size based on measured gain error in a memory (44). The gain-adjusted LSB size is applied to the digital filter to cause gain-adjusted LSB size values to be added to or subtracted from accumulated content of the digital filter in accordance with a first or second state, respectively, of the comparator (30) during each cycle of the ADC. The final accumulated content after all required cycles of the ADC is a gain-corrected digital output signal (Dout(gain-corrected)).