db.collection.storageSize()

db.collection. storageSize ( )

Returns:	The total amount of storage allocated to this collection for document storage. If collection data is compressed (which is the default for WiredTiger), the storage size reflects the compressed size and may be smaller than the value returned by db.collection.dataSize().

Provides a wrapper around the storageSize field of the collStats (i.e. db.collection.stats()) output.