How much it holds depends upon what camera you are using and what resolution the camera is set to.
You can estimate it in this manner:
If your camera has an 8 megapixel sensor, and is taking .jpg photos, you can divide 4 gig by 4 meg and get an approximate answer.
(.jpg photos are compressed files, approx 1/2 the size of the sensor capacity)
4 gig is 4,000,000,000
4 meg is 4,000,000
for an answer of at least 1,000 photos.
The memory card in the advertisement is a good brand and at a very good price.
how much does a 4 gig memory hold? how many pictures will it take?
and i found this on amazon...it says it's marked down by $173 and only costs $46.99. is this cheap for a memory card?