diff --git a/CHANGELOG.md b/CHANGELOG.md
index b54340a56a..2c42808d8c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#5777](https://github.com/thanos-io/thanos/pull/5777) Receive: Allow specifying tenant-specific external labels in Router Ingestor.
 - [#6352](https://github.com/thanos-io/thanos/pull/6352) Store: Expose store gateway query stats in series response hints.
 - [#6420](https://github.com/thanos-io/thanos/pull/6420) Index Cache: Cache expanded postings.
+- [#6441](https://github.com/thanos-io/thanos/pull/6441) Compact: Compactor will set `index_stats` in `meta.json` file with max series and chunk size information.
 
 ### Fixed
 
diff --git a/cmd/thanos/downsample.go b/cmd/thanos/downsample.go
index 5b2dbfeca7..366eb16145 100644
--- a/cmd/thanos/downsample.go
+++ b/cmd/thanos/downsample.go
@@ -385,10 +385,29 @@ func processDownsampling(
 		"from", m.ULID, "to", id, "duration", downsampleDuration, "duration_ms", downsampleDuration.Milliseconds())
 	metrics.downsampleDuration.WithLabelValues(m.Thanos.GroupKey()).Observe(downsampleDuration.Seconds())
 
-	if err := block.VerifyIndex(logger, filepath.Join(resdir, block.IndexFilename), m.MinTime, m.MaxTime); err != nil && !acceptMalformedIndex {
+	stats, err := block.GatherIndexHealthStats(logger, filepath.Join(resdir, block.IndexFilename), m.MinTime, m.MaxTime)
+	if err == nil {
+		err = stats.AnyErr()
+	}
+	if err != nil && !acceptMalformedIndex {
 		return errors.Wrap(err, "output block index not valid")
 	}
 
+	meta, err := metadata.ReadFromDir(resdir)
+	if err != nil {
+		return errors.Wrap(err, "read meta")
+	}
+
+	if stats.ChunkMaxSize > 0 {
+		meta.Thanos.IndexStats.ChunkMaxSize = stats.ChunkMaxSize
+	}
+	if stats.SeriesMaxSize > 0 {
+		meta.Thanos.IndexStats.SeriesMaxSize = stats.SeriesMaxSize
+	}
+	if err := meta.WriteToDir(logger, resdir); err != nil {
+		return errors.Wrap(err, "write meta")
+	}
+
 	begin = time.Now()
 
 	err = block.Upload(ctx, logger, bkt, resdir, hashFunc)
diff --git a/pkg/block/block_test.go b/pkg/block/block_test.go
index b373124122..6d977d3044 100644
--- a/pkg/block/block_test.go
+++ b/pkg/block/block_test.go
@@ -142,7 +142,7 @@ func TestUpload(t *testing.T) {
 		testutil.Equals(t, 4, len(bkt.Objects()))
 		testutil.Equals(t, 3727, len(bkt.Objects()[path.Join(b1.String(), ChunksDirname, "000001")]))
 		testutil.Equals(t, 401, len(bkt.Objects()[path.Join(b1.String(), IndexFilename)]))
-		testutil.Equals(t, 546, len(bkt.Objects()[path.Join(b1.String(), MetaFilename)]))
+		testutil.Equals(t, 567, len(bkt.Objects()[path.Join(b1.String(), MetaFilename)]))
 
 		// File stats are gathered.
 		testutil.Equals(t, fmt.Sprintf(`{
@@ -181,7 +181,8 @@ func TestUpload(t *testing.T) {
 			{
 				"rel_path": "meta.json"
 			}
-		]
+		],
+		"index_stats": {}
 	}
 }
 `, b1.String(), b1.String()), string(bkt.Objects()[path.Join(b1.String(), MetaFilename)]))
@@ -192,7 +193,7 @@ func TestUpload(t *testing.T) {
 		testutil.Equals(t, 4, len(bkt.Objects()))
 		testutil.Equals(t, 3727, len(bkt.Objects()[path.Join(b1.String(), ChunksDirname, "000001")]))
 		testutil.Equals(t, 401, len(bkt.Objects()[path.Join(b1.String(), IndexFilename)]))
-		testutil.Equals(t, 546, len(bkt.Objects()[path.Join(b1.String(), MetaFilename)]))
+		testutil.Equals(t, 567, len(bkt.Objects()[path.Join(b1.String(), MetaFilename)]))
 	}
 	{
 		// Upload with no external labels should be blocked.
@@ -224,7 +225,7 @@ func TestUpload(t *testing.T) {
 		testutil.Equals(t, 8, len(bkt.Objects()))
 		testutil.Equals(t, 3727, len(bkt.Objects()[path.Join(b2.String(), ChunksDirname, "000001")]))
 		testutil.Equals(t, 401, len(bkt.Objects()[path.Join(b2.String(), IndexFilename)]))
-		testutil.Equals(t, 525, len(bkt.Objects()[path.Join(b2.String(), MetaFilename)]))
+		testutil.Equals(t, 546, len(bkt.Objects()[path.Join(b2.String(), MetaFilename)]))
 	}
 }
 
diff --git a/pkg/block/metadata/meta.go b/pkg/block/metadata/meta.go
index 787a03c241..89ce68c1a2 100644
--- a/pkg/block/metadata/meta.go
+++ b/pkg/block/metadata/meta.go
@@ -90,6 +90,14 @@ type Thanos struct {
 
 	// Rewrites is present when any rewrite (deletion, relabel etc) were applied to this block. Optional.
 	Rewrites []Rewrite `json:"rewrites,omitempty"`
+
+	// IndexStats contains stats info related to block index.
+	IndexStats IndexStats `json:"index_stats,omitempty"`
+}
+
+type IndexStats struct {
+	SeriesMaxSize int64 `json:"series_max_size,omitempty"`
+	ChunkMaxSize  int64 `json:"chunk_max_size,omitempty"`
 }
 
 type Rewrite struct {
diff --git a/pkg/block/metadata/meta_test.go b/pkg/block/metadata/meta_test.go
index 0be53197e8..94de50da64 100644
--- a/pkg/block/metadata/meta_test.go
+++ b/pkg/block/metadata/meta_test.go
@@ -31,7 +31,8 @@ func TestMeta_ReadWrite(t *testing.T) {
 		"downsample": {
 			"resolution": 0
 		},
-		"source": ""
+		"source": "",
+		"index_stats": {}
 	}
 }
 `, b.String())
@@ -73,6 +74,10 @@ func TestMeta_ReadWrite(t *testing.T) {
 				Downsample: ThanosDownsample{
 					Resolution: 123144,
 				},
+				IndexStats: IndexStats{
+					SeriesMaxSize: 2000,
+					ChunkMaxSize:  1000,
+				},
 			},
 		}
 		testutil.Ok(t, m1.Write(&b))
@@ -121,7 +126,11 @@ func TestMeta_ReadWrite(t *testing.T) {
 			{
 				"rel_path": "meta.json"
 			}
-		]
+		],
+		"index_stats": {
+			"series_max_size": 2000,
+			"chunk_max_size": 1000
+		}
 	}
 }
 `, b.String())
@@ -199,7 +208,8 @@ func TestMeta_ReadWrite(t *testing.T) {
 				"rel_path": "index",
 				"size_bytes": 1313
 			}
-		]
+		],
+		"index_stats": {}
 	}
 }
 `, b.String())
diff --git a/pkg/compact/compact.go b/pkg/compact/compact.go
index 585d5d6b4d..69aa553713 100644
--- a/pkg/compact/compact.go
+++ b/pkg/compact/compact.go
@@ -818,7 +818,7 @@ func outOfOrderChunkError(err error, brokenBlock ulid.ULID) OutOfOrderChunksErro
 	return OutOfOrderChunksError{err: err, id: brokenBlock}
 }
 
-// IsOutOfOrderChunk returns true if the base error is a OutOfOrderChunkError.
+// IsOutOfOrderChunkError returns true if the base error is a OutOfOrderChunkError.
 func IsOutOfOrderChunkError(err error) bool {
 	_, ok := errors.Cause(err).(OutOfOrderChunksError)
 	return ok
@@ -1100,28 +1100,45 @@ func (cg *Group) compact(ctx context.Context, dir string, planner Planner, comp
 	bdir := filepath.Join(dir, compID.String())
 	index := filepath.Join(bdir, block.IndexFilename)
 
-	newMeta, err := metadata.InjectThanos(cg.logger, bdir, metadata.Thanos{
-		Labels:       cg.labels.Map(),
-		Downsample:   metadata.ThanosDownsample{Resolution: cg.resolution},
-		Source:       metadata.CompactorSource,
-		SegmentFiles: block.GetSegmentFiles(bdir),
-	}, nil)
-	if err != nil {
-		return false, ulid.ULID{}, errors.Wrapf(err, "failed to finalize the block %s", bdir)
+	if err := os.Remove(filepath.Join(bdir, "tombstones")); err != nil {
+		return false, ulid.ULID{}, errors.Wrap(err, "remove tombstones")
 	}
 
-	if err = os.Remove(filepath.Join(bdir, "tombstones")); err != nil {
-		return false, ulid.ULID{}, errors.Wrap(err, "remove tombstones")
+	newMeta, err := metadata.ReadFromDir(bdir)
+	if err != nil {
+		return false, ulid.ULID{}, errors.Wrap(err, "read new meta")
 	}
 
+	var stats block.HealthStats
 	// Ensure the output block is valid.
 	err = tracing.DoInSpanWithErr(ctx, "compaction_verify_index", func(ctx context.Context) error {
-		return block.VerifyIndex(cg.logger, index, newMeta.MinTime, newMeta.MaxTime)
+		stats, err = block.GatherIndexHealthStats(cg.logger, index, newMeta.MinTime, newMeta.MaxTime)
+		if err != nil {
+			return err
+		}
+		return stats.AnyErr()
 	})
 	if !cg.acceptMalformedIndex && err != nil {
 		return false, ulid.ULID{}, halt(errors.Wrapf(err, "invalid result block %s", bdir))
 	}
 
+	thanosMeta := metadata.Thanos{
+		Labels:       cg.labels.Map(),
+		Downsample:   metadata.ThanosDownsample{Resolution: cg.resolution},
+		Source:       metadata.CompactorSource,
+		SegmentFiles: block.GetSegmentFiles(bdir),
+	}
+	if stats.ChunkMaxSize > 0 {
+		thanosMeta.IndexStats.ChunkMaxSize = stats.ChunkMaxSize
+	}
+	if stats.SeriesMaxSize > 0 {
+		thanosMeta.IndexStats.SeriesMaxSize = stats.SeriesMaxSize
+	}
+	newMeta, err = metadata.InjectThanos(cg.logger, bdir, thanosMeta, nil)
+	if err != nil {
+		return false, ulid.ULID{}, errors.Wrapf(err, "failed to finalize the block %s", bdir)
+	}
+
 	// Ensure the output block is not overlapping with anything else,
 	// unless vertical compaction is enabled.
 	if !cg.enableVerticalCompaction {
diff --git a/pkg/compact/compact_e2e_test.go b/pkg/compact/compact_e2e_test.go
index 9b40da16dc..9a798ece61 100644
--- a/pkg/compact/compact_e2e_test.go
+++ b/pkg/compact/compact_e2e_test.go
@@ -399,6 +399,8 @@ func testGroupCompactE2e(t *testing.T, mergeFunc storage.VerticalChunkSeriesMerg
 			testutil.Assert(t, labels.Equal(extLabels, labels.FromMap(meta.Thanos.Labels)), "ext labels does not match")
 			testutil.Equals(t, int64(124), meta.Thanos.Downsample.Resolution)
 			testutil.Assert(t, len(meta.Thanos.SegmentFiles) > 0, "compacted blocks have segment files set")
+			// Only one chunk will be generated in that block, so we won't set chunk size.
+			testutil.Assert(t, meta.Thanos.IndexStats.SeriesMaxSize > 0, "compacted blocks have index stats series max size set")
 		}
 		{
 			meta, ok := others[groupKey2]
@@ -415,6 +417,8 @@ func testGroupCompactE2e(t *testing.T, mergeFunc storage.VerticalChunkSeriesMerg
 			testutil.Assert(t, labels.Equal(extLabels2, labels.FromMap(meta.Thanos.Labels)), "ext labels does not match")
 			testutil.Equals(t, int64(124), meta.Thanos.Downsample.Resolution)
 			testutil.Assert(t, len(meta.Thanos.SegmentFiles) > 0, "compacted blocks have segment files set")
+			// Only one chunk will be generated in that block, so we won't set chunk size.
+			testutil.Assert(t, meta.Thanos.IndexStats.SeriesMaxSize > 0, "compacted blocks have index stats series max size set")
 		}
 	})
 }