Azure Cosmos DB RU Calculator

RU/s = reads × (1 RU per KB) + writes × (5 RU per KB) + queries × RU per query, rounded up to the next 100; cost = RU/s ÷ 100 × rate × 730 × regions, ×1.5 on autoscale and ×2 with multi-region writes. Cosmos DB normalises every operation into request units: a 1 KB point read is 1 RU, a 1 KB write about 5 RU because of index maintenance, and queries are whatever the request-charge header reports. Autoscale bills 1.5× the standard rate but only for the RU/s actually used between 10% and 100% of your maximum, so it wins when the peak-to-average ratio is worse than about 1.5.

Provisioned throughput is billed per region every hour whether you use it or not, so an over-provisioned container replicated to three regions with multi-region writes costs six times what the numbers suggest — verify the per-100-RU/s rate for your region and API in the Azure pricing calculator.

This calculator takes 12 inputs: Point reads per second, Writes per second, Average item size, Queries per second, RU per query, Throughput mode, Average autoscale utilisation, Regions, Multi-region writes enabled, Price per 100 RU/s, Transactional storage, Storage price per GB. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.