The size of an audio file is determined by two factors, the audio compression format and the bit rate that have been used to encode the audio file. The most important to remember is that higher bit rates leads to larger file sizes but also to higher audio quality.

Calculating a song’s file size for the MP3, AAC and WMA audio formats are relatively easy. You just need to multiply the standard bit rate for each audio format by 60 seconds for receiving the file size for one minute.

The standard bit rate for the MP3 audio format is 128 Kbps, for the AAC audio format is 96 Kbps and for the WMA audio format is 64 Kbps. An approximate table over how many music minutes, songs, music hours and the number of CDs that each memory card capacity can hold can be found below. General information about memory capacity can be found at memory card storage capacity.

Memory Card	Number of	Number of	Number of	Audio
Capacity	Minutes	Songs	Hours or CDs	Format
	63	16	1	MP3
64 MB	84	21	1.5	AAC
	125	31	2	WMA
	125	31	2	MP3
128 MB	167	42	3	AAC
	251	63	4	WMA
	251	63	4	MP3
256 MB	334	84	6	AAC
	501	125	8	WMA
	501	125	8	MP3
512 MB	668	167	12	AAC
	1003	251	16	WMA
	1003	251	16	MP3
1 GB	1337	334	24	AAC
	2005	501	32	WMA
	2005	501	32	MP3
2 GB	2674	668	48	AAC
	4011	1003	64	WMA
	4011	1003	64	MP3
4 GB	5348	1336	96	AAC
	8022	2006	128	WMA

We assume that each song is 4 minutes long and each CD contains 60 minutes of music or consists of 15, a 4 minute, songs. The MB and GB terms may be misleading since the exact amount of bytes is not exactly what the terms are indicating. The correct conversions can be found here. It is important to have in mind that approximately 6 % of a memory card's listed capacity is used for memory management, and therefore is not be available for data storage. This has been taken in consideration in the above calculations.

Generally speaking:
1 MB = 1 minute MP3 music
A 64 MB memory card stores the equivalent of one audio CD or one hour of music.

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