Estimate Google Cloud Pub/Sub costs based on message volume and delivery.
Last verified: April 2026
Total messages published per day across all topics
Minimum billable size is 1 KB per message
Each subscription receives a copy of every message, multiplying delivery cost
Retained messages incur storage at $0.27/GB/month
Output will appear here...The estimator computes monthly data volume by multiplying message count by average message size (with 1 KB minimum enforcement), then multiplies by the number of subscriptions for delivery volume. It applies the per-TiB publishing and delivery rates, subtracts the 10 GiB free tier, and adds any snapshot/seek storage costs based on retained message volume and retention period.
The GCP Pub/Sub Cost Estimator calculates monthly costs based on message volume, message size, and the number of subscriptions. Pub/Sub pricing includes charges for message ingestion, delivery, and snapshot/seek storage. The tool accounts for the free tier, message size minimums (1 KB minimum per publish), and the multiplication effect of multiple subscriptions on delivery costs.
Your microservice architecture has a central event topic with 8 subscriptions. At 5 million messages per day averaging 2 KB each, the estimator reveals that delivery costs are 8x publishing costs because every subscription receives every message. You realize 3 of the subscriptions only need a subset of events. By adding message filtering attributes, those 3 subscriptions reduce their delivery volume by 80%, cutting your total Pub/Sub bill by 30%.
Push subscriptions deliver messages to an HTTPS endpoint automatically, but pull subscriptions give you more control over backpressure and batching. For cost optimization, use pull with large batch sizes (up to 1,000 messages) to reduce the number of API calls and minimize per-request overhead.
Every Pub/Sub message has a minimum billable size of 1 KB. If you publish thousands of tiny messages (like IoT sensor readings at 50 bytes each), you are paying 20x more per byte than necessary. Batch small messages client-side before publishing to dramatically reduce costs.
Dead letter topics are essential for production but they create a second delivery charge. A message that fails 5 delivery attempts and lands in the dead letter topic generates 6 delivery charges total. Set your maxDeliveryAttempts thoughtfully to balance reliability against cost.
Pub/Sub charges per TiB of data published and delivered. The first 10 GiB per month is free. Publishing costs apply once per message, while delivery costs apply per subscription. A message delivered to 5 subscriptions incurs 5x the delivery charge. The minimum billable message size is 1 KB.
Each publish and delivery operation is billed at a minimum of 1 KB, even if the actual message is smaller. If you publish many small messages (e.g., 100 bytes each), batching them into larger messages can significantly reduce costs by avoiding the 1 KB minimum per publish.
Pub/Sub Lite offers zonal messaging at lower cost with per-partition throughput and storage capacity reservations instead of pay-per-message pricing. It requires capacity planning but can be 5-10x cheaper for high-throughput workloads. The trade-off is zonal (not regional) availability and manual scaling.
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