From a3294b5aa22d89a86b6483a837c1e925a7d91c09 Mon Sep 17 00:00:00 2001
From: Max Kotliar <mkotlyar@victoriametrics.com>
Date: Fri, 3 Apr 2026 21:20:01 +0300
Subject: [PATCH] docs/guide: fix free space calculation factor in capacity
 planning formula

Replace 1.2 multiplier with 1.25 in disk space estimation formula.

1.2 only provides ~16.7% free space, while the docs recommend keeping
20%. Using 1.25 correctly accounts for 20% free space.

Inspired by
https://github.com/VictoriaMetrics/VictoriaMetrics/pull/10394
---
 docs/guides/understand-your-setup-size/README.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/guides/understand-your-setup-size/README.md b/docs/guides/understand-your-setup-size/README.md
index a61733bfd7..b16ec24a7a 100644
--- a/docs/guides/understand-your-setup-size/README.md
+++ b/docs/guides/understand-your-setup-size/README.md
@@ -125,7 +125,7 @@ As a reference, see resource consumption of VictoriaMetrics cluster on our [play
 The Retention Period is the number of days or months for storing data. It affects the disk space usage.
 The formula for calculating required disk space is the following:
 ```
-Bytes Per Sample * Ingestion rate * Replication Factor * (Retention Period in Seconds +1 Retention Cycle(day or month)) * 1.2 (recommended 20% of free space for merges ) 
+Bytes Per Sample * Ingestion rate * Replication Factor * (Retention Period in Seconds +1 Retention Cycle(day or month)) * 1.25 (recommended 20% of free space for merges ) 
 ```
 
 The **Retention Cycle** is one **day** or one **month**. If the retention period is higher than 30 days cycle is a month; otherwise day.
@@ -143,7 +143,7 @@ Keep at least **20%** of free space for VictoriaMetrics to remain efficient with
 
 A Kubernetes environment that produces 5k time series per second with 1-year of the Retention Period and ReplicationFactor=2:
 
-`(1 byte-per-sample * 5000 time series * 2 replication factor * 34128000 seconds) * 1.2 ) / 2^30 = 381 GB`
+`(1 byte-per-sample * 5000 time series * 2 replication factor * 34128000 seconds) * 1.25 ) / 2^30 = 397 GB`
 
 VictoriaMetrics requires additional disk space for the index. The lower Churn Rate, the lower is disk space usage for the index.
 Usually, index takes about **20%** of the disk space for storing data. High cardinality setups may use **>50%** of storage size for index. If your indexdb looks unexpectedly large, see [FAQ: Why indexdb size is so large?](https://docs.victoriametrics.com/victoriametrics/faq/#why-indexdb-size-is-so-large) for typical ratios and troubleshooting tips.