DynamoDB Capacity Calculator Tool - RCU/WCU and Monthly Cost Estimator

First Published:
Last Updated:

Estimate Amazon DynamoDB capacity requirements and compare Provisioned vs On-Demand monthly costs entirely in your browser.

All calculations are performed entirely in your browser using client-side JavaScript. No data is transmitted to any server. Your workload parameters never leave your device.

  • This tool is provided "AS IS" without any warranties of any kind.
  • Pricing data is bundled and may be outdated. Refer to the official AWS pricing page for current rates before making purchasing decisions.
  • Estimates assume 730 hours per month and 100% Provisioned utilization. Auto Scaling, reserved capacity, free tier, Global Tables replicated WCU, DAX, and Streams costs are not included.
  • Figures are rough estimates only; actual AWS bills will differ based on real traffic patterns, metered usage, and additional services.
  • By using this tool, you accept full responsibility for any outcomes.

This tool uses client-side JavaScript for all processing. No data is transmitted to servers, no files are uploaded online, all processing happens locally in your browser. Once loaded, this tool continues to work even without an internet connection. For more details, please refer to our Web Tools Disclaimer.

Workload Presets

Item & Region

Read Workload

Write Workload

Storage & Backup

Estimated Capacity & Monthly Cost

Pricing region: US East (N. Virginia)
Required RCU / sec
0
1 RRU per read
Required WCU / sec
0
1 WRU per write
Provisioned / month
$0.00
100% utilization
On-Demand / month
$0.00
per request pricing

Provisioned Capacity

Compute (RCU + WCU)$0.00
Storage + PITR$0.00
On-Demand Backup$0.00
Total / month$0.00

On-Demand

Compute (RRU + WRU)$0.00
Storage + PITR$0.00
On-Demand Backup$0.00
Total / month$0.00
Enter workload values to see a recommendation.

Features

  • RCU / WCU Calculation: Computes required capacity units per second from item size, request rate, and consistency model using official DynamoDB rounding rules (4 KB for reads, 1 KB for writes).
  • Provisioned vs On-Demand: Side-by-side monthly cost comparison with a clear break-even recommendation.
  • Consistency Models: Supports Eventually Consistent (0.5×), Strongly Consistent (1×), and Transactional (2×) reads, plus Standard and Transactional writes.
  • Multi-Region Pricing: Seven commonly used AWS regions bundled — N. Virginia, Oregon, Ireland, Frankfurt, Tokyo, Singapore, Mumbai.
  • Storage & Backup: Includes Storage, Point-In-Time Recovery (PITR), and On-Demand Backup cost components.
  • Workload Presets: One-click Small IoT, Medium E-Commerce, and Large Logging scenarios for quick sanity checks.
  • Live Recalculation: Every result updates instantly as you type — no submit button.
  • Privacy First: 100% client-side JavaScript. Works offline once loaded.

How to Use

  1. Either click a Workload Preset or enter your workload manually.
  2. Set the Average Item Size (in bytes or KB) and the target AWS Region.
  3. Enter expected Reads per second and choose the consistency model.
  4. Enter expected Writes per second and choose Standard or Transactional.
  5. Enter Stored Data size and optionally enable PITR or add On-Demand Backup size.
  6. Review the Provisioned vs On-Demand comparison and the recommendation at the bottom.
  7. Click Copy Summary to capture a plain-text report for design docs or tickets.

Important Notes

  • Pricing data is bundled and may be outdated. Always verify with the official AWS DynamoDB pricing page before making decisions.
  • Provisioned cost assumes 100% utilization for 730 hours/month. Real workloads with Auto Scaling will typically cost less.
  • RCU rounds item size up to the nearest 4 KB; WCU rounds up to the nearest 1 KB. Items under 1 byte still consume 1 unit minimum.
  • Transactional operations consume 2× the base capacity units because DynamoDB uses a two-phase protocol.
  • Not modeled (MVP limitations): Global Tables replicated WCU, DAX cluster costs, DynamoDB Streams, Standard-IA table class, Reserved Capacity, free tier, and data transfer costs.
  • Storage and PITR both use a per-GB-month price; on-demand backup uses a separate lower per-GB-month rate.

References:
Tech Blog with curated related content
Web Tools Collection

Written by Hidekazu Konishi