pg_relation_size in mb
SELECT
schema_name,
relname,
pg_size_pretty(table_size) AS size,
table_size
FROM (
SELECT
pg_catalog.pg_namespace.nspname AS schema_name,
relname,
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
WHERE schema_name NOT LIKE 'pg_%'
ORDER BY table_size DESC;