# Sizing Amazon OpenSearch Service domains
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There's no perfect method of sizing Amazon OpenSearch Service domains. However, by starting with an understanding of your storage needs, the service, and OpenSearch itself, you can make an educated initial estimate on your hardware needs. This estimate can serve as a useful starting point for the most critical aspect of sizing domains: testing them with representative workloads and monitoring their performance.

**Topics**
+ [Calculating storage requirements](bp-storage.md)
+ [Choosing the number of shards](bp-sharding.md)
+ [Choosing instance types and testing](bp-instances.md)