What is a Request Unit (RU) in Cosmos DB?

A Request Unit is a normalized measure of throughput that abstracts CPU, memory, and IOPS. A point read of a 1 KB document costs 1 RU. Writes, queries, and larger documents consume more RUs. You provision a certain number of RU/s and every operation deducts from that budget.

How does autoscale differ from manual provisioned throughput?

Manual provisioned throughput gives you a fixed RU/s allocation that you adjust yourself. Autoscale automatically scales between 10% and 100% of a maximum RU/s you set, and you pay for the peak consumed in each hour. Autoscale costs up to 50% more per RU/s at peak but avoids throttling during traffic spikes.

Does the calculator account for multi-region writes?

Yes. When multi-region writes are enabled, write RU consumption is multiplied by the number of regions. The calculator lets you specify the number of write regions to reflect this in the cost estimate.

Azure Cosmos DB RU Calculator

StorageAzure

Calculate Cosmos DB Request Units (RU/s) based on operation types and document sizes.

Cosmos DB Configuration

Document Size (KB)

Reads/sec

Writes/sec

Queries/sec

Query Complexity

Indexing Policy

Capacity Mode

Multi-Region Writes

Raw Output

Output will appear here...

About This Tool

The Azure Cosmos DB RU Calculator helps you estimate the Request Units per second (RU/s) your Cosmos DB workload will consume based on document sizes, operation types, indexing policies, and query complexity. Cosmos DB charges by provisioned or consumed RU/s, making accurate RU estimation critical for both performance and cost management. Enter your read, write, and query patterns to get a recommended RU/s provision and estimated monthly cost across manual and autoscale throughput modes. The calculator also covers serverless Cosmos DB pricing for intermittent workloads, helping you choose the most economical capacity model.

When to Use This Tool

•Sizing provisioned RU/s for a new microservice that performs a known mix of point reads, upserts, and cross-partition queries.
•Comparing manual provisioned throughput versus autoscale for workloads with variable traffic patterns.
•Estimating whether serverless Cosmos DB is cheaper than provisioned throughput for low-traffic or dev/test workloads.
•Calculating the RU impact of adding a secondary index or changing the indexing policy on a high-volume container.

Frequently Asked Questions

What is a Request Unit (RU) in Cosmos DB?: A Request Unit is a normalized measure of throughput that abstracts CPU, memory, and IOPS. A point read of a 1 KB document costs 1 RU. Writes, queries, and larger documents consume more RUs. You provision a certain number of RU/s and every operation deducts from that budget.
How does autoscale differ from manual provisioned throughput?: Manual provisioned throughput gives you a fixed RU/s allocation that you adjust yourself. Autoscale automatically scales between 10% and 100% of a maximum RU/s you set, and you pay for the peak consumed in each hour. Autoscale costs up to 50% more per RU/s at peak but avoids throttling during traffic spikes.
Does the calculator account for multi-region writes?: Yes. When multi-region writes are enabled, write RU consumption is multiplied by the number of regions. The calculator lets you specify the number of write regions to reflect this in the cost estimate.

Disclaimer: This tool runs entirely in your browser. No data is sent to our servers. Always verify outputs before using them in production. AWS, Azure, and GCP are trademarks of their respective owners.