WAV and FLAC keep every sample the recorder captured. MP3, AAC (in M4A), Opus and Vorbis throw away what a model of human hearing says you will not miss, and cannot give it back. That single distinction decides most of the choices on these pages. Converting FLAC to MP3 is a reasonable one-way trip for a portable player; converting MP3 to WAV makes a much larger file that sounds exactly the same, and is worth doing only when some piece of software refuses MP3 outright.

Bitrate, in numbers you can use

Stereo WAV at CD quality runs about 10 MB per minute. MP3 at 192 kbps is about 1.4 MB per minute and is, for most people on most equipment, indistinguishable from the source. Speech does not need anything like that: 96 kbps, in mono, halves it again with no meaningful loss, which is the right setting for a lecture, an interview or a podcast. 320 kbps genuinely pays only when the source is lossless, because there are no earlier compression artefacts being preserved at great expense.

Editing before converting

If you are going to trim, adjust the level or join files together, do it while the audio is still in its highest-quality form and convert once at the end. Every lossy encode is another round of discarding, and although a single hop is inaudible, a chain of them is not. Audio work is also much faster than video work, because there are no pictures to decode, so most of these tools finish in seconds even on a long file.