Practical guide
Build a GCP egress forecast from traffic data
Turn bytes into a useful GCP egress estimate by grouping traffic by source, destination, service path, and month.
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Start with measured byte buckets
An egress forecast starts with bytes, not revenue or request count. Export one representative month of network usage and group each flow by source product, source location, destination type, and destination location. Google documents different paths for intra-location, inter-region, Interconnect, and internet transfer.
If a service sends 4 TiB to internet clients, 1 TiB to a cross-region database, and 500 GiB through Interconnect, retain three line items. Next month, multiply each by its own growth assumption—say 1.2, 1.0, and 1.5—not one global percentage. The arithmetic is simple but exposes whether customer delivery, replication, or hybrid integration drives the forecast.
Check service-specific prices before attaching rates. Cloud NAT adds processing; CDN has cache lookup, fill, and delivery; load balancing can charge processed data. Deduplicate bytes only after establishing exactly which pricing component bills the path. Compare the forecast to a billing export and revise unknown destinations before treating it as a commitment decision.
Use the GCP Network Egress Calculator for its Standard Tier internet-out Iowa scenario. Related calculators for NAT, CDN, and load balancing cover additional components.
FAQ
Can request count replace bytes?
Only if response-size distributions are stable and measured; bytes are the billing-relevant quantity.
Should growth use peak traffic?
Use baseline, expected, and peak scenarios instead of silently treating peak as every month.