A capacitance-to-time converter (CTC) that measures the change in capacitance ΔC of a differential-type capacitive sensor (DCS) is presented in this letter. Most of the existing measurement circuits for DCS assumes its offset capacitance ( C01 and C02 ) be exactly matched. While in practical cases, it is difficult to have matched offset capacitance ( C01=C02 ) due to sensor structure or manufacturing defects. This mismatch ( C01≠C02 ) will introduce a noticeable error in output of existing schemes. Moreover, the conversion time for most of these schemes are large, which is not suitable for high-speed applications. The proposed CTC implements a closed-loop system that generates a pulse width-modulated output whose on -time is proportional to ΔC . It implements an automatic offset-mismatch nullification (AOFN) process that eliminates the effect of mismatch between the offset capacitances of DCS. The developed prototype of CTC showed a worst-case linearity error of 0.3% for ΔC in a range of ± 180 pF and a conversion time of 2 ms. This result demonstrates the usefulness of the CTC for accurate and high-speed measurement applications.