Understanding Cloud Data Transfer Costs
Data transfer costs are often the most surprising element of cloud bills. While compute and storage pricing is well understood, egress charges can quickly accumulate and represent a significant portion of total cloud spend. This guide explains how data transfer pricing works and strategies to optimize these costs.
Types of Data Transfer
Ingress (Data In)
Data transferred INTO the cloud is typically free across all major providers:
- Uploading files to storage
- Incoming API requests
- Data migration to cloud
Egress (Data Out)
Data transferred OUT of the cloud incurs charges:
- Serving content to users
- API responses
- Backup downloads
- Data exports
Internal Transfer Types
| Transfer Type | AWS | GCP | Azure |
|---|---|---|---|
| Same AZ | Free | Free | Free |
| Cross-AZ (same region) | $0.01/GB | $0.01/GB | Free* |
| Cross-Region | $0.02-0.09/GB | $0.01-0.08/GB | $0.02-0.08/GB |
*Azure charges for cross-AZ in some configurations
Internet Egress Pricing
AWS Data Transfer Out
| Tier | Volume/Month | Price/GB |
|---|---|---|
| Free Tier | First 100 GB | Free (12 months) |
| Tier 1 | Up to 10 TB | $0.09 |
| Tier 2 | 10-50 TB | $0.085 |
| Tier 3 | 50-150 TB | $0.07 |
| Tier 4 | 150+ TB | $0.05 |
Google Cloud Egress
| Destination | Volume | Price/GB |
|---|---|---|
| Worldwide | 0-1 TB | $0.12 |
| Worldwide | 1-10 TB | $0.11 |
| Worldwide | 10+ TB | $0.08 |
| Australia/China | Any | $0.19 |
Azure Bandwidth
| Zone | Volume | Price/GB |
|---|---|---|
| Zone 1 (US, EU) | 5 GB-10 TB | $0.087 |
| Zone 1 | 10-50 TB | $0.083 |
| Zone 1 | 50-150 TB | $0.07 |
| Zone 2 (Asia, AU) | Any | $0.12-0.19 |
CDN Cost Savings
How CDNs Reduce Costs
- Lower egress rates: CDN egress is often cheaper than direct
- Caching: Reduces origin server egress
- Edge locations: Serve from closer locations
- Bundled pricing: CDNs often include bandwidth
CDN Pricing Comparison
| CDN | Price Range/GB | Notes |
|---|---|---|
| CloudFront | $0.085-0.02 | Tiered pricing, free tier |
| Cloudflare | $0 (plans) | Unlimited bandwidth on paid plans |
| Fastly | $0.12-0.08 | Pay-as-you-go |
| Akamai | Custom | Enterprise pricing |
CDN Savings Example
10 TB monthly egress with 85% cache hit rate:
- Direct AWS egress: 10,000 GB x $0.09 = $900
- With CloudFront: Origin (1,500 GB x $0.02) + CDN (10,000 GB x $0.085) = $880
- With Cloudflare Pro ($20/mo): $20 flat + origin egress = ~$50
Cost Optimization Strategies
1. Use CDNs for Static Content
- Cache static assets (images, JS, CSS)
- Set appropriate cache headers
- Use CDN with best pricing for your volume
2. Architect for Data Locality
- Keep data and compute in same AZ when possible
- Use regional services appropriately
- Consider multi-region only when needed
3. Compress Data
- Enable gzip/brotli compression
- Optimize image formats (WebP, AVIF)
- Minimize API response payloads
4. Negotiate Enterprise Agreements
- Committed use discounts available at scale
- AWS has Private Pricing for high volume
- Consider multi-cloud for negotiating leverage
5. Use Free Tier Strategically
- AWS: 100 GB/month free for 12 months
- GCP: Egress to GCP services often free
- Cloudflare: Unlimited CDN on Pro plan
Hidden Data Transfer Costs
Often Overlooked
- NAT Gateway: $0.045/GB processed on AWS
- VPN/Direct Connect: Additional per-GB charges
- Load Balancer: Data processing charges
- API Gateway: Per-request and data charges
- Lambda: Response payload egress
Cross-Cloud Transfer
- Multi-cloud architectures incur egress from each cloud
- Consider dedicated interconnects for high volume
- Google Cloud has free egress to some destinations
Monitoring Data Transfer
AWS
- Cost Explorer with "Data Transfer" filter
- VPC Flow Logs for detailed analysis
- CloudWatch metrics for real-time monitoring
GCP
- Billing reports with network egress breakdown
- VPC Flow Logs
- Network Intelligence Center
Azure
- Cost Management + Billing
- Network Watcher
- Bandwidth usage in portal
Conclusion
Data transfer costs can be a significant and often surprising portion of cloud bills. By understanding the pricing tiers, leveraging CDNs appropriately, and architecting for data locality, you can significantly reduce these costs. Use our calculator to compare costs across providers and evaluate CDN options for your specific data transfer patterns.