While loading a large database from files to a Postgres schema, I found very useful to know how much space on disk it actually occupies (just in case I need to re-size the disk). I found this answer online:

SELECT schema_name,
    pg_size_pretty(sum(table_size)::bigint) as "disk space",
    (sum(table_size) / pg_database_size(current_database())) * 100
        as "percent"
FROM (
      SELECT pg_catalog.pg_namespace.nspname as schema_name,
          pg_relation_size(pg_catalog.pg_class.oid) as table_size
      FROM   pg_catalog.pg_class
          JOIN pg_catalog.pg_namespace
              ON relnamespace = pg_catalog.pg_namespace.oid
) t
GROUP BY schema_name
ORDER BY schema_name

Which results in a list like:

postgres-info]

HTH,

PS: All credit goes to this StackOverflow answer!