Par Meter displays real-time peak levels, RMS levels and the ratio between the two known as "PAR" or peak-to-average ratio. This ratio is an indicator of the subjective "loudness" of an audio program.
In addition to real-time displays, Par Meter also gives running status of the total file data from the last reset. A manual reset button, "clear all", is provided so that the cumulative data can be reset at any point while audio is running.
Par Meter costs $15 and is available for Windows as a VST effect plug-in (it must be used as a "master insert" and will not work as a "send effect").