How much space do I need to download this app on my iPhone?

My iPHone doesn't have a lot of space left, and i need to download an 893 MB app. (its called miku miku flick)
in the settings part in my phone, its says i have 1.2 GB left. When i try downloading the app, its says i don't have enough space to download it. Why does it do that? Isn't 1.2 GB 1200 MB?

The amount of space left isn't always accurate. My iPhone says I have 2.5 GB left. When accurately I have about 1.5 GB left. So you're iPhone may only have around 0.2 GB left. 893 is equivalent to 0.87 GB. So you don't have enough space for the app to be transferred. The only way to get it on is to take off an app that isn't important or you don't use on a daily basis. Hope this helped!