Check your iCloud storage usage on iCloud.com
You can use Settings on iCloud.com to see how much iCloud storage you have and how much is available. You can see a bar graph that shows how much storage various categories of data use, such as iOS and iPadOS device backups, photos and videos, documents and data stored in iCloud, and email messages and attachments.
In Settings on iCloud.com, look at the Storage section.
For information about a segment of the bar graph, tap the segment to see its name and numeric storage size above the graph.