I have paid for 200 GB cloud storage but I am running out of storage on my iPad but if i delete from my iPad it is also deleted from iCloud on all my devices

I agree why pay for 200GB when I can't use the 193.3 bites I still have? It always makes me delete photos when I want to take a picture. This is really unnecessary but I want to know why I have to pay for storage I can't even use.

Storage in iCloud is different than storage on the iPhone/iPad. Purchasing storage in iCloud makes no difference to the storage on the iOS devices. That storage is fixed and cannot be added to. iCloud storage is different. You need free space on the iOS device to take a photo.

With iCloud photo enabled, you cannot delete a photo on one device without deleting it from every device that uses iCloud photo library. In order to save space on your mobile devices (and indeed your Mac if you wish to do so) turn on optimisation for photos on these devices (settings > photos & camera > optimise storage on your mobile device and Photo preferences > optimise storage on your Mac)

Optimisation is dynamic, it reduces the resolution of your photos as and when needed, so you may not notice it occurring at first. However when it is needed, it is very effective and users have reported libraries being optimised to much less than 10% of their original size in some cases. My own library is about 9% of its original size on my phone.

You won't have to delete anything, I've already explained that the process is dynamic and it won't start swapping out original photos for low resolution photos until it needs to. Either you aren't yet in danger of running out of space or the process has already started swapping out originals for optimised versions and you just haven't noticed

I am having the exact same issue and came here for this reason as well. I also have my photos set to optimize and I am still getting notifications that my storage is almost full on my phone when I have 154 GB available on iCloud storage. I was under the impression that the photos would automatically save onto iCloud and not locally, but my photo library is still taking up 3.8 GB on my phone. What gives???

3.8 GB doesn't exactly tell me a lot on it's own.

My library for example uses 4 GB but in full resolution uses over 40 GB on the Mac, that suggests to me that optimisation works rather well.

Ooooh. I finally get it. My photo library takes up 37.4GB so about 10% of that is 3.8 GB, which is whats on my phone. I was under the impression that with iCloud Photo Library enabled that it would only store the photos on iCloud and not take up any space on my phone.