How many pictures 4 gb hold on a 16.2 mp DSLR?

I'm getting a Nikon D5100 and was wondering if I could use my other camera's memory card which is 4 gb. Or get a higher one.

The 4g card will do fine if you shoot jpegs. If you shoot RAW, it will still work, but you will want to get a second card if you do a lot of shooting.

Format it before using it
if it is not a class 10
I would buy a new one

A handful of 4 gb cards are better than using larger ones.

Why? Because larger cards can make the photographer lazy so they do not copy all their images to their computer at the end of each shooting day (all of your eggs in one basket kind of thing).

Memory cards are not primary storage or backup devices. Once all the images are safely on your computer, format the memory card using the format feature on the camera

I'm not sure of the exact number for a Nikon but my Pentax K5 with the same 16.2 mp sensor holds just over a100 RAW images, or 268 JPEGs at full size.

You can use your other camera's memory cards. It might be a good idea to make to format the card in the D5100 before you use it to ensure there are no funny file structure conflicts.

http://aviewfinderdarkly.com.au

*** update

According to the user manual the Nikon D5100 holds about 170 RAW images on a 4g card and 420 full size jpegs.