Loudness Unit Meter Portable is a stand-alone LU meter for windows based on FFmpeg.
All you need to do is download FFmpeg and put it in the same folder as Lump 1.1.

For a much (much!) better result, you can now use Youlean from
I created LUMP as a test, before Youlean existed...

Important note about limitations:

- Works ONLY on "Stereo Mix"!
First, Stereo Mix needs to be enabled.
Second, the main sound card (same as Stereo Mix) must be the one playing the sound you want to measure.

- Please allow FFmpeg to start (in the background). The initial delay depends on how quick FFmpeg can start producing measurements.

The displayed Loudness and True Peak are not calibrated, or better said, depends on what your system "Full Scale" is.
However, you can count on LUMP to indicate if your output volume has a consistant Loudness. That is the whole point.