diff --git a/Project.toml b/Project.toml
index cd813eba..94a94ccd 100644
--- a/Project.toml
+++ b/Project.toml
@@ -10,6 +10,7 @@ CodecLz4 = "5ba52731-8f18-5e0d-9241-30f10d1ec561"
 CodecXz = "ba30903b-d9e8-5048-a5ec-d1f5b0d4b47b"
 CodecZlib = "944b1d66-785c-5afd-91f1-9de20f533193"
 CodecZstd = "6b39b394-51ab-5f42-8807-6242bab2b4c2"
+IterTools = "c8e1da08-722c-5040-9ed9-7db0dc04731e"
 LRUCache = "8ac3fa9e-de4c-5943-b1dc-09c6b5f20637"
 LorentzVectors = "3f54b04b-17fc-5cd4-9758-90c048d965e3"
 Memoization = "6fafb56a-5788-4b4e-91ca-c0cea6611c73"
diff --git a/src/UnROOT.jl b/src/UnROOT.jl
index 2e58975c..9c08e5cb 100644
--- a/src/UnROOT.jl
+++ b/src/UnROOT.jl
@@ -10,6 +10,7 @@ import AbstractTrees: children, printnode, print_tree
 
 using CodecZlib, CodecLz4, CodecXz, CodecZstd, StaticArrays, LorentzVectors, ArraysOfArrays
 using Mixers, Parameters, Memoization, LRUCache
+import IterTools: groupby
 
 import Tables, TypedTables, PrettyTables
 
diff --git a/src/iteration.jl b/src/iteration.jl
index 0ff09b13..67766c78 100644
--- a/src/iteration.jl
+++ b/src/iteration.jl
@@ -307,3 +307,29 @@ end
 function Base.getindex(ba::LazyBranch{T,J,B}, rang::UnitRange) where {T,J,B}
     return [ba[i] for i in rang]
 end
+
+_clusterranges(t::LazyTree) = _clusterranges([getproperty(t,p) for p in propertynames(t)])
+function _clusterranges(lbs::AbstractVector{<:LazyBranch})
+    basketentries = [lb.b.fBasketEntry[1:numbaskets(lb.b)+1] for lb in lbs]
+    common = mapreduce(Set, ∩, basketentries) |> collect |> sort
+    return [common[i]+1:common[i+1] for i in 1:length(common)-1]
+end
+_clusterbytes(t::LazyTree; kw...) = _clusterbytes([getproperty(t,p) for p in propertynames(t)]; kw...)
+function _clusterbytes(lbs::AbstractVector{<:LazyBranch}; compressed=false)
+    basketentries = [lb.b.fBasketEntry[1:numbaskets(lb.b)+1] for lb in lbs]
+    common = mapreduce(Set, ∩, basketentries) |> collect |> sort
+    bytes = zeros(Float64, length(common)-1)
+    for lb in lbs
+        b = lb.b
+        finflate = compressed ? 1.0 : b.fTotBytes/b.fZipBytes
+        entries = b.fBasketEntry[1:numbaskets(b)+1]
+        basketbytes = b.fBasketBytes[1:numbaskets(b)+1] * finflate
+        iclusters = searchsortedlast.(Ref(common), entries[1:end-1])
+        pairs = zip(iclusters, basketbytes)
+        sumbytes = [sum(last.(g)) for g in groupby(first, pairs)]
+        bytes .+= sumbytes
+    end
+    return bytes
+end
+
+Tables.partitions(t::LazyTree) = (t[r] for r in _clusterranges(t))
diff --git a/test/runtests.jl b/test/runtests.jl
index 6038efa1..d7d54ac9 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -690,3 +690,15 @@ end
     @test (UnROOT.basketarray_iter(t.b1) .|> length) == [1228, 1228, 44]
     @test length(UnROOT.basketarray(t.b1, 1)) == 1228
 end
+
+@testset "Cluster ranges" begin
+    t = LazyTree(UnROOT.samplefile("tree_with_clusters.root"),"t1");
+    @test all(UnROOT._clusterbytes(t; compressed=true) .< 10000)
+    @test all(UnROOT._clusterbytes(t; compressed=false) .< 10000)
+    @test UnROOT._clusterbytes([t.b1,t.b2]) == UnROOT._clusterbytes(t)
+    @test length(UnROOT._clusterranges([t.b1])) == 157
+    @test length(UnROOT._clusterranges([t.b2])) == 70
+    @test length(UnROOT._clusterranges(t)) == 18 # same as uproot4
+    @test sum(UnROOT._clusterbytes([t.b1]; compressed=true)) == 33493.0 # same as uproot4
+    @test sum(UnROOT._clusterbytes([t.b2]; compressed=true)) == 23710.0 # same as uproot4
+end
diff --git a/test/samples/tree_with_clusters.py b/test/samples/tree_with_clusters.py
new file mode 100644
index 00000000..8b83fd2c
--- /dev/null
+++ b/test/samples/tree_with_clusters.py
@@ -0,0 +1,19 @@
+#!/usr/bin/env python
+import ROOT as r
+
+f = r.TFile("tree_with_clusters.root", "recreate")
+t = r.TTree("t1","t1")
+v1 = r.vector("int")()
+v2 = r.vector("int")()
+t.Branch("b1", v1, 500) # default bufsize is 32000, but making sure
+t.Branch("b2", v2, 1000) # default bufsize is 32000, but making sure
+t.SetAutoFlush(10000)
+for irow in range(2500):
+    v1.clear()
+    v2.clear()
+    for e in [irow+q for q in range(2)]:
+        v1.push_back(e)
+        v2.push_back(e+1)
+    t.Fill()
+t.Write()
+f.Close()
diff --git a/test/samples/tree_with_clusters.root b/test/samples/tree_with_clusters.root
new file mode 100644
index 00000000..77483150
Binary files /dev/null and b/test/samples/tree_with_clusters.root differ