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Amazon RDS pricing calculator
A monthly RDS for PostgreSQL or MySQL bill split into the instance, its storage, backups and the Extended Support fee an old engine version pays, with what the same database costs with a Multi-AZ standby (or without one) and one size down.
What does a small RDS PostgreSQL database cost? (US East, On-Demand, prices checked 2026-10-20)
A db.t4g.medium (2 vCPU, 4 GiB) with 100 GB of gp3 storage, running all month, costs $58.95: $47.45 for the instance and $11.50 for the storage. Turn on Multi-AZ and it becomes $117.17 ($94.17 + $23.00), because you pay for a standby instance and a second copy of the disk.
Estimated monthly RDS bill
$0
US East (N. Virginia), RDS for PostgreSQL and MySQL (the same hourly prices for these classes), On-Demand, from aws.amazon.com/rds/postgresql/pricing, aws.amazon.com/rds/mysql/pricing and the AWS Price List API, checked 2026-10-20; Extended Support re-checked 2026-11-07: $0.10 per vCPU-hour in years 1 and 2 past the end of standard support and $0.20 in year 3, billed for the standby too on Multi-AZ, not covered by Reserved Instances. Multi-AZ with one standby costs about twice the Single-AZ hourly rate (each list price, e.g. $0.065 and $0.129 an hour for db.t4g.medium); gp3 storage is $0.115 per GB-month Single-AZ and $0.23 Multi-AZ; backup storage up to the size of your provisioned storage is free, then $0.095 per GB-month; T4g CPU credits in Unlimited mode are $0.075 per vCPU-hour. Extra gp3 IOPS and throughput, data transfer out, RDS Proxy, Performance Insights retention and Reserved Instances are not included.
Why the RDS line grows
The instance is most of the bill, and it runs whether anyone queries it or not. RDS charges per hour the instance exists, so a database sized for launch day keeps paying for launch day. Open CloudWatch for the instance and look at a normal week of CPUUtilization and FreeableMemory before you change anything. If CPU sits under 20% and plenty of memory is free, one class down halves that line, and the "one size down" row above shows what it would save.
Multi-AZ doubles everything it touches. You pay for a standby instance in a second zone and for a second copy of the storage, which is why it is the first thing we check on a startup's bill. It is worth it for a production database you can't afford to lose for an hour. It is rarely worth it for staging, preview or analytics copies, and those are often where we find it switched on.
The burstable classes (db.t4g) have a trap. They earn CPU credits while idle and spend them under load, and RDS creates them in Unlimited mode, so a database that runs hot all day keeps buying credits at $0.075 per vCPU-hour on top of the instance price. Once that line shows up every month, a db.m7g of the same size is usually cheaper and faster.
Storage is the line nobody shrinks. You pay for provisioned gigabytes, not used ones, and RDS storage can grow but can't be made smaller in place. Snapshots kept by hand outside the retention window count as backup storage once they exceed the free allowance. And an old major version past its standard support date adds Extended Support per vCPU-hour, which can cost more than the instance itself: every RDS for MySQL 8.0 database started paying it on August 1, 2026 (what the fee adds and how to find it).
Putting a cache in front of the database to take reads off it? The ElastiCache pricing calculator prices one on Valkey and on Redis OSS, nodes or Serverless. On AWS the Valkey version is the cheaper of the two by 20% or more.
If your RDS line is bigger than this page says it should be, send us the bill. We read it line by line for free, and moving a small database off RDS is sometimes the cheapest fix of all (how we move databases to EU providers).