diff --git a/docs/_docs/monitoring-metrics/new-metrics-system.adoc b/docs/_docs/monitoring-metrics/new-metrics-system.adoc
index 0c0a49e204bab..0a1bfd9b8ffe6 100644
--- a/docs/_docs/monitoring-metrics/new-metrics-system.adoc
+++ b/docs/_docs/monitoring-metrics/new-metrics-system.adoc
@@ -276,6 +276,8 @@ The metric is called `TotalAllocatedSize`.
 
 You can also get an estimate of the actual size of data by multiplying the number of link:memory-architecture#data-pages[data pages] in use by the fill factor. The fill factor is the ratio of the size of data in a page to the page size, averaged over all pages. The number of pages in use and the fill factor are available at the level of data <<Data Region Size,region metrics>>.
 
+For link:memory-configuration/data-regions[data region] metrics, Ignite also exposes the `SizeUsedByData` metric. It estimates how many bytes are currently occupied by data in the region, including the empty space inside non-empty pages. Use this metric when you need a more direct estimate of how much data is stored in the region, and use `TotalAllocatedSize` when you need to monitor how much space has already been allocated for that region.
+
 Add up the estimated size of all data regions to get the estimated total amount of data on the node.
 
 
@@ -323,6 +325,7 @@ The size of the data region on a node comprises the size of all partitions (incl
 | Attribute | Type | Description | Scope
 
 | TotalAllocatedSize | long  | The size of the space allocated for this data region (in bytes). {allocsize_note} | Node
+| SizeUsedByData | long | The estimated number of bytes occupied by data in this data region, including empty space inside non-empty pages. | Node
 | PagesFillFactor| float | The average amount of data in pages as a ratio of the page size. | Node
 | TotalUsedPages | long | The number of data pages that are currently in use. | Node
 | PhysicalMemoryPages |long |The number of data pages in this data region held in RAM. | Node
diff --git a/docs/_docs/monitoring-metrics/new-metrics.adoc b/docs/_docs/monitoring-metrics/new-metrics.adoc
index 0850d9ae33116..2611d0ccc35ee 100644
--- a/docs/_docs/monitoring-metrics/new-metrics.adoc
+++ b/docs/_docs/monitoring-metrics/new-metrics.adoc
@@ -406,6 +406,7 @@ Register name: `io.dataregion.{data_region_name}`
 |PagesWritten|    long|    Number of pages written from last restart.
 |PhysicalMemoryPages| long|    Number of pages residing in physical RAM.
 |PhysicalMemorySize | long|    Gets total size of pages loaded to the RAM, in bytes
+|SizeUsedByData| long|    Estimated number of bytes occupied by data in the region, including empty space inside non-empty pages.
 |TotalAllocatedPages |long|    Total number of allocated pages.
 |TotalAllocatedSize|  long  |  Gets a total size of memory allocated in the data region, in bytes
 |TotalThrottlingTime| long|    Total throttling threads time in milliseconds. The Ignite throttles threads that generate dirty pages during the ongoing checkpoint.