Azure Bandwidth & Egress Cost Calculator

Egress is any data transfer that leaves the Azure boundary. Inbound data — from the internet, from on-premises, from partners — is free. Within a single region (e.g., between a VM and a nearby storage account in UK South), traffic is free. Egress is charged only when data crosses the Azure edge: to the internet, to on-premises, or to another Azure region.

The calculator distinguishes between internet egress (outside Azure entirely) and inter-region egress (between Azure regions). Both are billable, but at different rates. Internet egress is more expensive because it uses public bandwidth; inter-region is cheaper because Microsoft's backbone handles it internally.

The first 100 GB of outbound internet transfer per month is free. Above that, pricing is tiered: per-GB rates drop as volume increases. The tiers are:

• 0–100 GB/month: Free
• 100–10,000 GB/month: ~£0.070/GB (higher per-GB rate)
• 10,000–50,000 GB/month: ~£0.067/GB (slight discount)
• 50,000–150,000 GB/month: ~£0.056/GB (meaningful discount)
• 150,000–500,000 GB/month: ~£0.040/GB (substantial discount)
• 500,000+ GB/month: contact Microsoft for volume pricing

The tiered model rewards usage scale but also means small egress charges accumulate slowly until they don't. A 95 GB/month pattern costs nothing; 105 GB/month costs £0.35. The marginal GB is expensive even though you're past the free tier.

Internet egress is data leaving Azure for external destinations: user downloads, API calls to third-party services, S3 backups to AWS, etc. This is tiered and more expensive.

Inter-region egress is traffic between two Azure regions (e.g., UK South to North Europe). This is charged at a flat rate (~£0.016/GB for intra-Europe transfer) and applies whether you're replicating storage, scaling web tier, or failing over a database.

The design implication is subtle: multi-region architectures for redundancy or performance are real cost drivers, not cost-free. A database replica in a second region incurs egress charges for replication traffic. A global load-balanced service pays egress for cross-region failover backhaul. Teams often don't model this until it's in the invoice.

Imagine a SaaS platform running in UK South serving 10,000 users worldwide:

• Primary API + database: UK South (intra-region traffic is free)
• Blob storage + CDN: UK South with Azure CDN
• Backup: Replicated nightly to North Europe (DR policy)
• Analytics: Aggregate logs shipped to US East for ML pipeline (third-party contract)

Egress breakdown:

• CDN origin shield cache misses to users: ~200 GB/month (tiered, mostly at £0.070/GB = £14/month)
• Backup replication to North Europe: ~50 GB/month (£0.016/GB = £0.80/month)
• Log shipment to US East: ~150 GB/month (tiered, at £0.070/GB = £10.50/month)
• Total: ~£25/month egress

This isn't huge, but it's material if the platform also has storage and compute costs. More importantly, the backup and analytics transfer were probably never explicitly budgeted or challenged during architecture review.

Keep replicas and backups in the same region when possible. A secondary database in the same region has zero egress cost; moving it to another region for DR incurs per-GB charges indefinitely.

Use CDN aggressively for static content. Cache misses hit your egress bill; caching strategy beats architectural change for cost reduction.

Route external integrations through ExpressRoute or private endpoints where possible.Some external API patterns can be moved inside your private network, reducing or eliminating public internet egress.

Batch and compress data before export. Moving logs, backups, or analytics data off-cloud should be deliberate: compress, deduplicate, and batch transfers to minimize raw GB shipped.

Does using Azure CDN avoid egress charges? No. CDN origin fetches from your storage account still count as egress. CDN reduces the number of _origin_ requests (cache hits), but each miss is still billable. The benefit is fewer total egress bytes, not zero egress.

Does ExpressRoute eliminate egress costs? For private Azure-to-on-premises traffic routed through ExpressRoute, charges are different (ExpressRoute billing applies) and internet egress is bypassed. But you're not replacing egress with free transfer — you're replacing it with ExpressRoute charges. For cloud-to-cloud or cloud-to-internet, egress still applies.

Can I reduce egress by choosing a different region? Not directly. Egress rates are the same for all Azure regions. However, choosing a region closer to your users reduces the _amount_ of CDN miss traffic, which reduces egress bytes and therefore cost.

What if I'm unsure whether traffic counts as egress? The rule is straightforward: if data leaves the Azure boundary (to the internet or to another cloud) or crosses a region boundary within Azure, it's egress and will be billed. Intra-region and inbound traffic is free. When in doubt, assume the conservative case and run the calculator.