AWS KMS Cost Calculator (keys + API requests)

Estimate KMS-style costs with a simple model: customer managed key-months plus request charges. Compare baseline vs peak request volume with your pricing.

Inputs

Customer managed keys (count)
KMS requests (per month)
Avg 114.22 req/sec. Total Encrypt/Decrypt/GenerateDataKey/etc. across services.
Price ($ / key-month)
Price ($ / 10k requests)
~$3.00 per 1M. Use your effective pricing mix.
Instances (avg)
KMS calls per instance / sec
Average Encrypt/Decrypt/GenerateDataKey calls.
Est 52,531,200 requests/month.
Scenario presets
Simplified estimate: key-months + request charges. Multi-region keys, custom key stores, and downstream service charges are excluded.

Results

Estimated monthly total
$950.00
Key-month charges
$50.00
Request charges
$900.00
Requests/month
300,000,000

How to get your inputs

  • Inputs: use billing exports, metrics, or logs to get real counts/GB where possible.
  • Units: convert throughput (Mbps) or rates (RPS) into monthly units when needed.
  • Scenarios: build a baseline and a high-usage scenario to avoid under-budgeting.

Result interpretation

  • Key-month charges are predictable; request charges scale with encryption-heavy workloads.
  • Spikes usually map to retries, re-encryption jobs, or bursting traffic.

Common mistakes

  • Using a single average and ignoring peak/incident scenarios.
  • Double-counting or missing adjacent line items (transfer, logs, retries).

Input checklist

  • Count keys by environment (prod, staging, dev).
  • Estimate request volume by service (S3, EBS, RDS, secrets).
  • Check for batch re-encryption or rotation jobs.

Advanced inputs to capture

  • Count keys and requests as separate drivers.
  • Break out encrypt, decrypt, and data key calls if volumes differ.
  • Model batch jobs or incident spikes as a peak scenario.
  • Account for client-side caching if you use it.

Scenario planning

Scenario Keys Requests Drivers
Baseline Configured Expected Steady workload
Peak Same High Incident/batch jobs

Validate after changes

  • Compare your estimate to the first real bill and adjust assumptions.
  • Track the primary driver metric (requests/GB/count) over time.

Next steps

Guides All calculators Guide: KMS pricing Guide: estimate KMS requests KMS request volume estimator Guide: reduce KMS costs S3 archive cost calculator
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Example scenario

  • 50 keys at $1/key-month and 300M requests/month at $0.03 per 10k requests.
  • Peak 220% scenario highlights incident-driven KMS spikes.

Included

  • Key-month charges from key count and $/key-month.
  • Request charges from requests/month and $ per 10k requests.
  • Baseline vs peak scenario table for request spikes.

Not included

  • Multi-region keys and custom key stores unless modeled separately.
  • Downstream service charges that generate KMS requests (S3, EBS, RDS, etc.).

How we calculate

  • Key cost = keys x $ per key-month.
  • Request cost = (requests per month / 10,000) x $ per 10k requests.
  • Total = key + request costs.

FAQ

Why can KMS costs be higher than expected?
KMS requests can be generated by many services (storage encryption, database encryption, secrets access). High-frequency operations and chatty workloads can create very large request volume.
What's the fastest way to reduce KMS spend?
Reduce request volume: avoid per-request encryption in hot paths when not needed, use envelope encryption appropriately, and fix retry loops that amplify KMS calls.

Related tools

Guide: KMS pricing Guide: estimate KMS requests Guide: reduce KMS costs KMS request volume estimator S3 archive cost calculator

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Disclaimer

Educational use only. Not legal, financial, or professional advice. Results are estimates based on the inputs and assumptions shown on this page. Verify pricing and limits with your providers and documentation.

Last updated: 2026-02-23