# Optimal JVM Heap size?
**URL:** https://discuss.elastic.co/t/optimal-jvm-heap-size/384106
**Category:** Elasticsearch
**Created:** [December 16, 2025, 9:46am UTC](https://discuss.elastic.co/t/optimal-jvm-heap-size/384106 "2025-12-16T09:46:02Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Aditya\_M](https://discuss.elastic.co/u/Aditya_M)
#### Post date: [December 16, 2025, 9:46am UTC](https://discuss.elastic.co/t/optimal-jvm-heap-size/384106/1 "2025-12-16T09:46:02Z")
Hi All,
I am looking for verification on the optimal JVM Heap size configuration for our production cluster.
We are running on physical nodes with **500 GB of RAM** each.
I have read two conflicting pieces of advice regarding heap sizing:
1. **The 50% Rule:** Set heap to 50% of available RAM
2. **The 31GB Limit:** Never set heap above ~31GB to maintain Compressed OOPs.
**My Query:**
Is strictly capping the heap at 31GB the correct approach for a 500GB node, or is there any scenario where a larger heap (e.g., 64GB+) is recommended?
Thanks in advance for the help!
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### Author:  [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)
#### Post date: [December 16, 2025, 11:26am UTC](https://discuss.elastic.co/t/optimal-jvm-heap-size/384106/2 "2025-12-16T11:26:59Z")
> [@Aditya\_M](#):
>
> - **The 50% Rule:** Set heap to 50% of available RAM
This is not an accurate summary of [the relevant page in the manual](https://www.elastic.co/docs/reference/elasticsearch/jvm-settings) (emphasis mine):
> Set `Xms` and `Xmx` to **no more than** 50% of the total memory available to each Elasticsearch node. […] The 50% guideline is intended as a safe **upper bound** on the heap size. You may find that **heap sizes smaller than this maximum** offer better performance, for instance by allowing your operating system to use a larger filesystem cache.