The switching time is one of the key parameters used to assess the performance of an electrochromic material or device. In spite of its importance, there is currently no standard for how this parameter is defined, and as a result, it is difficult to compare switching time data between different research groups, and to quantify and assess reported improvements. We propose a standard method for reporting electrochromic switching times, based on straightforward experimental fittings resulting in an analytical expression that can directly correlate obtainable optical contrast values with their corresponding switching times. This analytical expression makes it possible to unambiguously define the performance of an electrochromic material or device using two parameters: a full switch contrast and a time constant.