diff --git a/tree/ntuple/v7/doc/BinaryFormatSpecification.md b/tree/ntuple/v7/doc/BinaryFormatSpecification.md
index 96565c818e9e1..2f894b586dd42 100644
--- a/tree/ntuple/v7/doc/BinaryFormatSpecification.md
+++ b/tree/ntuple/v7/doc/BinaryFormatSpecification.md
@@ -1049,8 +1049,8 @@ This section summarizes default settings of `RNTupleWriteOptions`.
 
 | Default                                | Value                        |
 |----------------------------------------|------------------------------|
-| Approximate Zipped Cluster             | 100 MB                       |
-| Max Unzipped Cluster                   | 1 GiB                        |
+| Approximate Zipped Cluster             | 128 MiB                      |
+| Max Unzipped Cluster                   | 1280 MiB                     |
 | Max Unzipped Page                      | 1 MiB                        |
 
 ## Glossary
diff --git a/tree/ntuple/v7/doc/tuning.md b/tree/ntuple/v7/doc/tuning.md
index c73cd914f8f3c..c49f13baff08b 100644
--- a/tree/ntuple/v7/doc/tuning.md
+++ b/tree/ntuple/v7/doc/tuning.md
@@ -5,7 +5,7 @@ A cluster contains all the data of a given event range.
 As clusters are usually compressed and tied to event boundaries, an exact size cannot be enforced.
 Instead, RNTuple uses a *target size* for the compressed data as a guideline for when to flush a cluster.
 
-The default cluster target size is 100 MB of compressed data.
+The default cluster target size is 128 MiB of compressed data.
 The default can be changed by the `RNTupleWriteOptions`.
 The default should work well in the majority of cases.
 In general, larger clusters provide room for more and larger pages and should improve compression ratio and speed.
@@ -13,7 +13,7 @@ However, clusters also need to be buffered during write and (partially) during r
 so larger clusters increase the memory footprint.
 
 A second option in `RNTupleWriteOptions` specifies the maximum uncompressed cluster size.
-The default is 1 GiB.
+The default is 10x the default cluster target size, i.e. ~1.2 GiB.
 This setting acts as an "emergency break" and should prevent very compressible clusters from growing too large.
 
 Given the two settings, writing works as follows:
diff --git a/tree/ntuple/v7/inc/ROOT/RNTupleWriteOptions.hxx b/tree/ntuple/v7/inc/ROOT/RNTupleWriteOptions.hxx
index 6626325b8bbb7..9ce2d60782bb6 100644
--- a/tree/ntuple/v7/inc/ROOT/RNTupleWriteOptions.hxx
+++ b/tree/ntuple/v7/inc/ROOT/RNTupleWriteOptions.hxx
@@ -61,10 +61,10 @@ public:
 protected:
    int fCompression{RCompressionSetting::EDefaults::kUseGeneralPurpose};
    /// Approximation of the target compressed cluster size
-   std::size_t fApproxZippedClusterSize = 100 * 1000 * 1000;
+   std::size_t fApproxZippedClusterSize = 128 * 1024 * 1024;
    /// Memory limit for committing a cluster: with very high compression ratio, we need a limit
    /// on how large the I/O buffer can grow during writing.
-   std::size_t fMaxUnzippedClusterSize = 1024 * 1024 * 1024;
+   std::size_t fMaxUnzippedClusterSize = 10 * fApproxZippedClusterSize;
    /// Initially, columns start with a page large enough to hold the given number of elements. The initial
    /// page size is the given number of elements multiplied by the column's element size.
    /// If more elements are needed, pages are increased up until the byte limit given by fMaxUnzippedPageSize