AWS · Free tool
AWS RDS cost calculator
The line item that doubles the day Multi-AZ ships. Plug in instance, storage, replicas, and commitment to see the real monthly bill plus a side-by-side against Aurora.
Estimated monthly RDS cost
$0
$0 per year
Instance + replicas
$0
primary 730 hr x $0.171/hr
Storage + IOPS
$0
500 GB x $0.115/GB-mo
Backup beyond free
$0
7 day retention
Multi-AZ premium
$0
vs single-AZ
Side-by-side vs Aurora
If your RDS bill looks high, check these first
- Multi-AZ on dev and staging environments.
- gp2 storage on databases that should be on gp3.
- No RI coverage on stable production instances.
- Read replicas left running after a load test.
- 35-day backup retention on databases over 1 TB.
- Manual snapshots retained forever after database deletion.
Why RDS bills double overnight
The day production goes Multi-AZ, instance and storage hours double. The day you add a read replica, instance hours go up another 100 percent. The day backup retention hits 14 days on a database large enough to exceed the free tier, the snapshot line shows up.
List every instance, flag gp2 storage, missing RI coverage, dev instances on Multi-AZ, and snapshots on dropped databases. The quiet doubler covers the full audit pattern.
Run this on your real account
Free 14-day audit, read-only IAM role, one-page CFO summary.
We pull every RDS and Aurora instance, flag missing RI coverage, gp2 holdouts, idle replicas, and orphan snapshots. The audit is free, the report is yours.
Frequently asked
Why does my RDS bill double when I enable Multi-AZ?
Multi-AZ provisions a hot standby instance in a second AZ and doubles instance hours and storage. The standby is not readable, so you also pay for read replicas if you want read scale. For dev and staging, Multi-AZ is rarely worth it. For production, the cost is the price of failover SLA.
Should I be on gp3 instead of gp2 for RDS storage?
Almost always yes. gp3 includes 12,000 IOPS and 250 MB/s for free at $0.115/GB-month. gp2 charges by volume size for IOPS at $0.10/GB-month with only 3 IOPS per GB. For most databases under 1 TB, the swap saves 15 to 30 percent on storage. The change is online with no downtime through ModifyDBInstance.
How much do Reserved Instances actually save on RDS?
A 1-year No Upfront RI saves about 30 percent on instance hours. 3-year All Upfront saves about 60 percent. Storage and backup are not eligible. RIs cover the standby on Multi-AZ and read replicas of the same class.
When does Aurora cost less than RDS, and when more?
Aurora Standard charges per I/O at $0.20 per million, plus $0.10/GB-month storage. For chatty workloads, Aurora I/O Optimized at $0.225/GB-month with no I/O charges is cheaper. RDS with gp3 stays cheaper for predictable, small databases under 100 GB.
How much backup storage is free?
Backup storage equal to your provisioned database storage is free. Past that, automated backups and manual snapshots cost $0.095/GB-month. Long retention windows on large databases are the most-missed line.
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