Elasticsearch Shard Calculator
Size Elasticsearch shards, replicas and node count for an index.
About Elasticsearch Shard Calculator
Shard size drives query performance: too small and coordination overhead dominates, too large and recovery and rebalancing become slow. Replicas multiply storage but are what allow the cluster to lose a node without data loss. Over-sharding is the most common Elasticsearch mistake, because each shard carries fixed heap and file handle costs regardless of how little data it holds.
Formula
Elasticsearch Shard
Primary shards = total data ÷ target shard size; total = primaries × (1 + replicas)
- target shard size
- Between 10 and 50 GB is the usual recommendation
- 80 per cent
- Elasticsearch watermarks block writes as disks fill, so plan to 80 per cent
Worked example
With the default values below, Elasticsearch Shard Calculator returns Primary Shards Required of 38. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Daily ingest volumeminimum 0 GB
- 50 GB
- Retention periodminimum 1 days
- 30 days
- Target shard sizeminimum 1 GB
- 40 GB
- Replicas per shardminimum 0
- 1
- Usable storage per nodeminimum 1 GB
- 1,000 GB
Results
- Primary Shards Required
- 38
- Primary Data Volume
- 1,500.00 GB
- Total Shards Including Replicas
- 76
- Total Storage Including Replicas
- 3,450.00 GB
- Nodes Required
- 5
Step by step
- 1Values used
- 2Elasticsearch Shard
- 3Primary Shards Required= 38
- 4Primary Data Volume= 1,500.00 GB
- 5Total Shards Including Replicas= 76
- 6Total Storage Including Replicas= 3,450.00 GB
- 7Nodes Required= 5
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or fees or charges into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Elasticsearch Shard calculated?
Primary shards = total data ÷ target shard size; total = primaries × (1 + replicas) Shard size drives query performance: too small and coordination overhead dominates, too large and recovery and rebalancing become slow. Replicas multiply storage but are what allow the cluster to lose a node without data loss.
Why does Elasticsearch Shard matter?
Over-sharding is the most common Elasticsearch mistake, because each shard carries fixed heap and file handle costs regardless of how little data it holds.
What values do I need to enter?
This calculator takes 5 inputs: Daily ingest volume, Retention period, Target shard size, Replicas per shard, Usable storage per node. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.