Quickest way to find out heroku database size

The new way seems to be:

heroku pg:info -a myapp

You'll see something like:

=== HEROKU_POSTGRESQL_PURPLE_URL (DATABASE_URL)
Plan:        Dev
Status:      available
Connections: 1
PG Version:  9.1.5
Created:     2012-10-19 01:27 UTC
Data Size:   12.1 MB
Tables:      31
Rows:        36068/10000 (Above limits, access disruption imminent)
Fork/Follow: Unavailable

Based on Nate's answer:

For shared DB w/o installing Postgres on your local machine

heroku console

ActiveRecord::Base.connection.execute("SELECT pg_size_pretty(pg_database_size('postgres'))").first

'postgres' is the name of my shared DB, when I put in template0 or template1 I get the same number back.