How many pictures are on a sdhc 4g card?

Now let's do some math...

4gb = 4x1024mb = 4096mb

4gb / 50mb = 4096mb / 50mb = 81.92

This means the 4gb card will hold 'bout 81 pictures.

If you ever need to know while on the go, you can round off a gig to 1000mb to give you an approximate answer to make the math easier.