diff --git a/src/ifcopenshell-python/ifcopenshell/util/unit.py b/src/ifcopenshell-python/ifcopenshell/util/unit.py
index 89e4466b6c..910efcd186 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/unit.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/unit.py
@@ -720,7 +720,29 @@ def calculate_unit_scale(ifc_file: ifcopenshell.file, unit_type: str = "LENGTHUN
             unit_scale *= conversion_factor.ValueComponent.wrappedValue
             unit = conversion_factor.UnitComponent
         if unit.is_a("IfcSIUnit"):
-            unit_scale *= get_prefix_multiplier(unit.Prefix)
+            prefix_multiplier = get_prefix_multiplier(unit.Prefix)
+            # An SI prefix attaches to the base unit symbol, and the prefixed
+            # symbol is raised to the power as a whole: dm3 = (dm)3 = 1e-3 m3,
+            # not 0.1 m3. For units whose dimensions are a pure power of length
+            # (METRE, SQUARE_METRE, CUBIC_METRE) the prefix multiplier must
+            # therefore be raised to the length exponent. Units with mixed or
+            # non-length dimensions (PASCAL, NEWTON, GRAM, ...) keep the linear
+            # multiplier, as there the prefix scales the derived unit itself.
+            # https://github.com/IfcOpenShell/IfcOpenShell/issues/9278
+            dimensions = unit.Dimensions
+            length_exponent = dimensions.LengthExponent
+            if length_exponent > 0 and not any(
+                (
+                    dimensions.MassExponent,
+                    dimensions.TimeExponent,
+                    dimensions.ElectricCurrentExponent,
+                    dimensions.ThermodynamicTemperatureExponent,
+                    dimensions.AmountOfSubstanceExponent,
+                    dimensions.LuminousIntensityExponent,
+                )
+            ):
+                prefix_multiplier **= length_exponent
+            unit_scale *= prefix_multiplier
     return unit_scale
 
 
diff --git a/src/ifcopenshell-python/test/util/test_unit.py b/src/ifcopenshell-python/test/util/test_unit.py
index 38d78ba024..0e3af2fc07 100644
--- a/src/ifcopenshell-python/test/util/test_unit.py
+++ b/src/ifcopenshell-python/test/util/test_unit.py
@@ -200,6 +200,31 @@ class TestCalculateUnitScale(test.bootstrap.IFC4):
         ifcopenshell.api.unit.assign_unit(self.file, units=[angle])
         assert subject.calculate_unit_scale(self.file, "PLANEANGLEUNIT") == pi / 180 * 0.001
 
+    def test_prefix_is_raised_to_the_length_exponent_for_area_and_volume(self):
+        # A prefixed square/cubic metre is (prefix-metre) squared/cubed:
+        # DECI SQUARE_METRE = dm2 = 1e-2 m2, DECI CUBIC_METRE = dm3 (litre) = 1e-3 m3.
+        # https://github.com/IfcOpenShell/IfcOpenShell/issues/9278
+        ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
+        area = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="AREAUNIT")
+        area.Prefix = "DECI"
+        volume = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="VOLUMEUNIT")
+        volume.Prefix = "DECI"
+        ifcopenshell.api.unit.assign_unit(self.file, units=[area, volume])
+        assert subject.calculate_unit_scale(self.file, "AREAUNIT") == pytest.approx(0.1**2)
+        assert subject.calculate_unit_scale(self.file, "VOLUMEUNIT") == pytest.approx(0.1**3)
+
+    def test_prefix_stays_linear_for_units_that_are_not_a_pure_power_of_length(self):
+        # For derived and non-length SI units the prefix scales the unit itself:
+        # KILO PASCAL = 1e3 Pa, KILO GRAM = 1e3 g.
+        ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
+        pressure = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="PRESSUREUNIT")
+        pressure.Prefix = "KILO"
+        mass = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="MASSUNIT")
+        mass.Prefix = "KILO"
+        ifcopenshell.api.unit.assign_unit(self.file, units=[pressure, mass])
+        assert subject.calculate_unit_scale(self.file, "PRESSUREUNIT") == pytest.approx(1000)
+        assert subject.calculate_unit_scale(self.file, "MASSUNIT") == pytest.approx(1000)
+
 
 class TestFormatLength(test.bootstrap.IFC4):
     def test_run(self):