Is the sim card the same for a samsung galaxy s3 and iphone 5?

I just bought an iphone 5 and I currently have a Samsung galaxy s3. When I go to activate the phone when it gets here do I need to get a new sim card or will I be able to use the same one to activate it?

I'm pretty sure they use the same size SIM card. And if for some reason it doesn't fit you can always ask your phone company for a replacement SIM card which should be free or only a few dollars.

Kelly, yes, positively the sim card is the same size.

I never owned an iphone but a friend of mine had one. I think they use a micro sim card.

The Galaxy S III uses a microSIM whereas the iPhone 5 uses a nanoSIM.

As far as activation it depends on if the iPhone 5 is locked to the carrier of the SIM you plan to use or unlocked. If neither then you're out of luck for now.