diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7dcfbea..4089805 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 All notable changes to PyTheory are documented here.
 
+## 0.36.5
+
+- **Duration arithmetic** — `Duration.WHOLE * 2`, `Duration.HALF + Duration.QUARTER`,
+  division, and reverse multiply all work now (previously raised TypeError)
+
 ## 0.36.3
 
 - **`Part.hold()`** — polyphonic overlap on a single part. Add notes
diff --git a/pyproject.toml b/pyproject.toml
index a5af92b..415bfdf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "pytheory"
-version = "0.36.4"
+version = "0.36.5"
 description = "Music Theory for Humans"
 readme = "README.md"
 license = "MIT"
diff --git a/pytheory/__init__.py b/pytheory/__init__.py
index dfc615c..b503552 100644
--- a/pytheory/__init__.py
+++ b/pytheory/__init__.py
@@ -1,6 +1,6 @@
 """PyTheory: Music Theory for Humans."""
 
-__version__ = "0.36.4"
+__version__ = "0.36.5"
 
 from .tones import Tone, Interval
 from .systems import System, SYSTEMS, TET
diff --git a/pytheory/rhythm.py b/pytheory/rhythm.py
index a5d9b9e..096e3f2 100644
--- a/pytheory/rhythm.py
+++ b/pytheory/rhythm.py
@@ -388,6 +388,24 @@ class Duration(Enum):
     DOTTED_QUARTER = 1.5
     TRIPLET_QUARTER = 2 / 3
 
+    # Arithmetic — lets you write ``Duration.WHOLE * 2`` → 8.0 beats.
+    def __mul__(self, other):
+        return self.value * other
+
+    def __rmul__(self, other):
+        return self.value * other
+
+    def __truediv__(self, other):
+        return self.value / other
+
+    def __add__(self, other):
+        if isinstance(other, Duration):
+            return self.value + other.value
+        return self.value + other
+
+    def __radd__(self, other):
+        return other + self.value
+
 
 class TimeSignature:
     """A musical time signature like 4/4 or 6/8."""
diff --git a/test_pytheory.py b/test_pytheory.py
index 3d518e2..4beb2ba 100644
--- a/test_pytheory.py
+++ b/test_pytheory.py
@@ -4869,6 +4869,19 @@ def test_duration_values():
     assert abs(Duration.TRIPLET_QUARTER.value - 2 / 3) < 1e-9
 
 
+def test_duration_arithmetic():
+    # Multiplication
+    assert Duration.WHOLE * 2 == 8.0
+    assert 2 * Duration.HALF == 4.0
+    assert Duration.QUARTER * 3 == 3.0
+    # Division
+    assert Duration.WHOLE / 2 == 2.0
+    # Addition
+    assert Duration.HALF + Duration.QUARTER == 3.0
+    assert Duration.HALF + 1.0 == 3.0
+    assert 1.0 + Duration.HALF == 3.0
+
+
 def test_time_signature_from_string_4_4():
     ts = TimeSignature.from_string("4/4")
     assert ts.beats == 4
diff --git a/uv.lock b/uv.lock
index 4ba03d4..5205f7d 100644
--- a/uv.lock
+++ b/uv.lock
@@ -698,7 +698,7 @@ wheels = [
 
 [[package]]
 name = "pytheory"
-version = "0.36.4"
+version = "0.36.5"
 source = { editable = "." }
 dependencies = [
     { name = "numeral" },