iOS Memory Limits

I'm working on an app that's using a lot of memory, and it looks like the limit on an iPad Air is 700 MB. I've been testing mostly on the Air because I believe it to be the worst case scenario in terms of memory and frame rate (that I have available for testing). I've gotten the memory usage down to around 610-620 MB, and that has prevented the out-of-memory crashes. And I've not run into any memory problems on other iOS devices I've tested on since reducing the size.

Is the limit of 700 MB constant across all iOS devices, or does it vary? Not a problem if it's higher, but I'm concerned that with some older iPhones that sill support iOS 12 it might be lower. Is there any way to tell how much free memory is available for my app? Application.lowMemory triggers a callback, but doesn't tell me how much memory is available/free.

 

If you are below 50% of system total RAM you should be fine.
I can see from my tests that things break when you go over the 70% limit (tried on different iphones and ipads)