Audio Converter

The WAV size is decided before you choose a file

WAV stores every sample at full width with no compression, so the output size is pure arithmetic: 44 bytes of header plus rate × channels × 2 bytes per second. At CD quality that is about 10 MB a minute whatever went in:

Which means the conversion ratio people quote is really a fact about the input. The same song grows by different amounts purely because the MP3 it came from was different:

Growing a file does not add anything to it

That is easy to say and easy to measure. Take a tone, reduce it to a given bit depth the way a lossy encoder would, then store it in a 16-bit WAV exactly as the converter above does, and count how many distinct sample values survive:

Same bytes on disk, 42 times the information in one of them. A 16-bit container writes two bytes per sample whether or not most of its range is reachable, so converting a lossy file to WAV buys you a larger file and nothing else. It is worth doing when you need an uncompressed format for editing; it is not worth doing to improve anything.

The MP3 path here has a related limit worth knowing about: it encodes at most two channels, so a surround source quietly arrives as stereo. 6 channels become 2, 8 channels become 2.

And no WAV can exceed four gigabytes

A WAV header records the length of the audio in a 32-bit field, which caps the whole format at 4 GB. Divide that by the data rate and you get a hard ceiling on duration:

Past that the field does not raise an error, it wraps. Writing 4,294,968,296 into a 32-bit slot stores 1,000, so a player reading the header sees a file claiming to be a kilobyte long. Recording a long meeting at 96 kHz reaches this in an afternoon, and nothing warns you on the way. If you need more, the formats that solve it are RF64 and W64, both of which widen exactly that one field.