How many GB will 400 photos take up on a IPhone?

Sunday (Easter Sunday) is my birthday and normally I'd have a barbecue with family and close firend but considering we're going to a rodeo for 4 days I decided to have a small get together then and take selfies/group photos with people for my birthday, then combine all those together and put them in a video for my birthday. I'm turning 16 so I really like this honestly. I don't want a massive party but just photos with people and small get together!
For those 4 days ill be at like 6 different locations, and I'll be taking selfies with people all day/night.
How many gb will that take up on my iPhone 4?
We're good friends with everyone there so I'm think roughly 400 photos per 2 nights, I'm taking my laptop so I can put the photos onto there to make more room.
I have roughly 2 gb on my phone free and it's a 5gb phone.
Cheers.

Happy birthday! And it might take 2.0 GB that's what mine took.

There are many variables that affect the file sizes of pictures, so there's no 100% correct answer to this question, only estimates. The iPhone 4 on average takes 2MB shots so 400 would take 800MB which is < a GB (1024MB). Should be even less than that since you are planning to use the front facing camera which takes lower resolution shots.