In electronic instrumentation and signal processing, a time to digital converter (abbreviated TDC) is a device for converting a signal of sporadic pulses into a digital representation of their time indices. Because the magnitude of the pulses are not usually measured, a TDC is used when the important information is to be found in the timing of events. In practice, a TDC usually follow a discriminator. TDCs are most often used in applications where measurement events happen infrequently, such as high energy physics experiments, where the sheer number of data channels in most detectors ensures that each channel will be excited only infrequently.

In its simplest implementation, a TDC is simply a high-frequency counter with a buffered output.