How is table size calculated?

Disk space is allocated per column because Redshift is a columnar data store. Within a table, each column is at least 1 MB. Each table also includes 3 system columns. Column sizes are multiplied by a replication factor, which is usually between 3 and 8.

The size increase is much more gradual after initial creation. You can read about Redshift cluster storage space on Amazon’s AWS knowledge center.