S3 replication cost: how to estimate cross-region replication

Replication is rarely "free". Even when the feature itself is simple, the bill usually combines a few different charges: data copied, extra replica storage, and sometimes request fees and transfer.

What volume should you count?

For most workloads, replication volume is closer to changed data than total stored data. If your bucket holds 20 TB but only 50 GB/day changes, your replication volume is driven by 50 GB/day (plus retries and overhead), not 20 TB.

Guide: estimate replication GB/month.

Exception: if you do a one-time migration/backfill (copying the whole bucket), model that as a separate one-time month: total copied GB plus any request/listing work needed to enumerate objects.

Replication cost components

  • Replication data (GB/month): bytes copied from source to destination.
  • Replica storage: you now store (almost) the same objects in a second location.
  • Requests: additional PUT/GET/LIST operations may be billed depending on provider/product.
  • Transfer: some setups effectively bill replication as cross-region transfer.

Fast estimation checklist

  1. Estimate changed data per day (GB/day), then multiply by ~30.4 to get GB/month.
  2. Price the per-GB replication line item with S3 replication cost calculator or storage replication cost calculator.
  3. Add replica storage with object storage cost calculator.
  4. If your provider bills this as transfer, price it with cross-region transfer cost.

CRR vs SRR (when choosing an option)

Cross-region replication (CRR) often adds transfer-like charges compared to same-region replication (SRR). Use this comparison checklist: S3 CRR vs SRR cost.

Common pitfalls

  • Counting the full bucket size: replication is driven by writes/changes.
  • Ignoring replica storage: storing a second copy can dominate monthly cost.
  • Request fees: many small objects can create high request volume.

How to validate (avoid billing surprises)

  • Validate replication GB/month from source write volume and churn (not from bucket size).
  • Validate directionality: which side is billed for transfer/feature fees depends on provider rules.
  • Validate object count and listing behavior for large buckets (LIST can be a real cost in migrations).
  • Validate that destination storage class matches your intent (defaulting to hot tier is common).

Related tools

S3 replication cost Storage replication cost Object storage cost Cross-region transfer

Educational use only. S3 and compatible services have provider-specific rules (directionality, request classes, minimums, and regional pricing). Use this as a planning framework and confirm details in official docs.

Sources

Related guides

Copy storage pricing: what you pay for when data moves
A practical guide to pricing storage copy operations (cross-region copy, replication, backups) across S3-like object storage: transfer, requests, and extra storage.
S3 CRR vs SRR cost: what changes (transfer, storage, requests)
A practical cost comparison of S3 cross-region replication (CRR) vs same-region replication (SRR). Compare transfer/feature fees, extra replica storage, and request costs - with calculators.
S3 pricing explained: storage vs requests vs egress
A practical breakdown of S3-like object storage pricing: GB-month storage, request fees, and data egress - plus how to estimate each without missing hidden line items.
S3 to Glacier transfer cost: what to include in the move
A practical checklist for S3 to Glacier transfer cost: transition requests, minimum storage duration, and any transfer or rewrite overhead.
Storage Costs Explained (GB-month, requests, retrieval)
A practical storage cost model: GB-month, requests, retrieval, and transfer. Includes estimation checklist.
S3 pricing: a practical model for storage, requests, egress, and replication
A practical S3 pricing guide: what to include (GB-month, requests, egress, replication) and how to estimate the key inputs without copying price tables.

Related calculators

Data Egress Cost Calculator
Estimate monthly egress spend from GB transferred and $/GB pricing.
API Response Size Transfer Calculator
Estimate monthly transfer from request volume and average response size.
VPC Data Transfer Cost Calculator
Estimate data transfer spend from GB/month and $/GB assumptions.
Cross-region Transfer Cost Calculator
Estimate monthly cross-region transfer cost from GB transferred and $/GB pricing.
RPS to Monthly Requests Calculator
Estimate monthly request volume from RPS, hours/day, and utilization.
API Request Cost Calculator
Estimate request-based charges from monthly requests and $ per million.

FAQ

What volume should I use for replication cost?
Use replicated GB/month based on changed data (writes and churn), not total stored bucket size, unless you're doing a one-time backfill.
Do I need to include destination storage?
Yes. Replication typically means storing data twice. Destination storage is often the biggest ongoing cost.
Is replication billed as transfer?
Sometimes. Replication can be billed as a per-GB feature fee, cross-region transfer, or both depending on provider and configuration. Model the per-GB line item and validate billing directionality.
Last updated: 2026-01-27