Why are app MB's so big on my Iphone?

[breeanavia]

Okay so I have a 8GB Iphone and its telling me that I don't have enough space on my Iphone to take a picture and I'm soooo confused because I don't even have any apps really. My mom has the same phone and has music and about 14 apps on her phone and 1.6GB of photos and her's is nowhere near full. When I go to my Usage it says this for each app I have:
Photos: 2.9GB
Instagram 921 MB
Poshmark 255 MB
Vine 153 MB
Yelp 108 MB
Pandora 57 MB
Dropbox 55MB
Pic Stitch 48MB
FallDown 24MB
Google Maps 16MG
BOA 6MB
Music/Videos no data

I'm so confused these app sizes are HUGE! When I search Instagram it says that its only 12.7MB and yet on my phone its 900!!!

Can someone please tell me what is wrong with my phone and how to get rid of this

[ScσττRΛSC³]

Using Instagram as an example

There is the app's size, 12.7MB & then there's the app's data, the difference between 921MB & 12.7MB.

Nothing is wrong with your phone. Just the way it is. You could use a computer app called PhoneClean to erase that out. No it will not clear out the pics you took or game/app progress etc. You may have to sign back into some apps though, Instagram is one of these, but you'd regain a ton of space doing so. Oh & its free for the record.