Is 16gb of space enough for the iPhone 5?

Ok I will have about a max of 300 apps. Around 250-300 songs (about 3-4 minutes long), and the rest will be pictures.

No if you have 300 apps and songs on your phone I would get the 64 gb

300 apps? You need more space. That's a lot of apps… You can't possible use that many on any regular basis, so you might consider 32 if you don't sync them all.

And this is an "Astronomy and Space" question, how?

For the music, I assume you are using iTunes which should tell you the exact amount of space your songs will take up. Or, you can find the music folder and view the properties to find the size. Or, if you are lazy we can approximate the average song at 3mb (300 songs x 3mb = 900mb, about 0.9gb).

As for the pictures, according to this article (source below) the iPhone 5 will take an average of 2.3mb per picture on high quality, so that's about 445 pictures per gigabyte!

Unfortunately, apps can't be given a dependable number as an average, as some can be as low as a few mb and some can be as large as a 1gb. But, you will have tons of room leftover for them.

@Nyx,
Because he has the word "space" in his question. And it's the astronomy and SPACE category right?

I'm where what happened to R&S sorry no wonder there were not any religious questions