Size backup storage from database size, retention window, daily change rate and manual snapshots, and price the billable excess.
Automated backups are one full baseline plus per-day incrementals of only the changed blocks, so retention multiplies the change rate rather than the database size — a 500 GB database changing 3% a day accrues about 15 GB per retained day, not 500 GB. AWS gives you backup storage equal to the total size of your databases free, so the bill is only what the retention window and manual snapshots push you past that line. The backup rate is an editable input with a realistic us-east-1 default, so confirm the current price with AWS for your region. Retention is the cheapest lever in a recovery plan and the easiest to get wrong in both directions: too short and you cannot recover from a slow-burn corruption, too long and you pay per GB-month for backups nobody will ever restore.
Database Backup
total backup = (full copy + size × daily change × retention days + snapshots × size × snapshot share) ÷ compression; billable = max(0, total − database size).
total backup = (full copy + size × daily change × retention days + snapshots × size × snapshot share) ÷ compression; billable = max(0, total − database size). Automated backups are one full baseline plus per-day incrementals of only the changed blocks, so retention multiplies the change rate rather than the database size — a 500 GB database changing 3% a day accrues about 15 GB per retained day, not 500 GB. AWS gives you backup storage equal to the total size of your databases free, so the bill is only what the retention window and manual snapshots push you past that line. The backup rate is an editable input with a realistic us-east-1 default, so confirm the current price with AWS for your region.
Retention is the cheapest lever in a recovery plan and the easiest to get wrong in both directions: too short and you cannot recover from a slow-burn corruption, too long and you pay per GB-month for backups nobody will ever restore.
This calculator takes 7 inputs: Database size, Automated backup retention, Data changed per day, Manual snapshots retained, Average manual snapshot size, Snapshot compression ratio, Backup storage price. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
Automated backups roll off at the end of the retention window, but a manual snapshot lives until you delete it — including after the database itself is deleted. They also do not benefit from the same incremental chain once the source database is gone.
The allowance is the total allocated size of your databases in that region, pooled — not a per-database figure. One database with a long retention window can consume the allowance earned by its quieter neighbours.