How to get a Firestore document size?

Question

From Firestore docs, we get that the maximum size for a Firestore document is:

Maximum size for a document 1 MiB (1,

Answer 1

The calculations used to compute the size of a document is fully documented here. There is a lot of text there, so please navigate there to read it. It's not worthwhile to copy all that text here.

If you're having to manually compute the size of a document as it grows, my opinion is that you're probably not modeling your data scalably. If you have lists of data that can grow unbounded, you should probably shouldn't be using an list field, and instead put that data in documents in a new collection or subcollection. There are some exceptions to this rule, but generally speaking, you should not have to worry about computing the size of a document in your client code.