diff --git a/ResSimpy/Units/Units.py b/ResSimpy/Units/Units.py
index ac19eb8be..7e8eb328d 100644
--- a/ResSimpy/Units/Units.py
+++ b/ResSimpy/Units/Units.py
@@ -72,6 +72,14 @@ def unit_system_enum_to_variable(self, unit_system: UnitSystem) -> str:
             case _:
                 raise ValueError(f'Unit system {unit_system} not recognised.')
 
+    def english_to_metbar(self, value: float) -> float:
+        """Converts the value from English to metbar."""
+        return value
+
+    def metbar_to_english(self, value: float) -> float:
+        """Converts the value from metbar to English."""
+        return value
+
 
 class Area(UnitDimension):
     """Units for area."""
@@ -340,6 +348,14 @@ class SurfaceRatesLiquid(UnitDimension):
     lab = 'stcc/hour'
     metric_atm = 'stm3/day'
 
+    def english_to_metbar(self, value: float) -> float:
+        """Converts the value from English to metbar."""
+        return value / 6.28981077
+
+    def metbar_to_english(self, value: float) -> float:
+        """Converts the value from metbar to English."""
+        return value * 6.28981077
+
 
 class SurfaceRatesGas(UnitDimension):
     """Units for surface rates gas."""
@@ -480,6 +496,14 @@ class Diameter(UnitDimension):
     lab = 'cm'
     metric_atm = 'cm'
 
+    def english_to_metbar(self, value: float) -> float:
+        """Converts the value from English to metbar."""
+        return value * 2.54
+
+    def metbar_to_english(self, value: float) -> float:
+        """Converts the value from metbar to English."""
+        return value / 2.54
+
 
 class HeatTransfer(UnitDimension):
     """Heat transfer units."""
diff --git a/ResSimpy/Units/convert_units.py b/ResSimpy/Units/convert_units.py
new file mode 100644
index 000000000..8e9c5f47f
--- /dev/null
+++ b/ResSimpy/Units/convert_units.py
@@ -0,0 +1,65 @@
+from typing import Callable, Optional, Protocol, TypeVar
+
+from ResSimpy.Enums.UnitsEnum import UnitSystem
+from ResSimpy.Units.AttributeMappings.BaseUnitMapping import BaseUnitMapping
+from ResSimpy.Units.Units import UnitDimension
+
+
+# Set up typing and generics for the convert_units function
+class UnitConvertableObject(Protocol):
+    """Protocol for objects that can be converted between unit systems.
+    Implements _unit_system and units properties.
+    """
+    _unit_system: UnitSystem
+
+    @property
+    def units(self) -> BaseUnitMapping: ...
+
+    @property
+    def unit_system(self) -> UnitSystem: ...
+
+
+T = TypeVar('T', bound=UnitConvertableObject)
+
+
+def get_map(from_unit: UnitSystem, to_unit: UnitSystem, unit_dim: UnitDimension) -> Optional[Callable]:
+    mapping = {'ENGLISH_METBAR': 'english_to_metbar',
+               'METBAR_ENGLISH': 'metbar_to_english',
+               }
+
+    function_name = mapping[from_unit.value + '_' + to_unit.value]
+
+    function_call = getattr(unit_dim, function_name, None)
+    if function_call is None:
+        return None
+    return function_call
+
+
+def convert_units(from_unit: UnitSystem, to_unit: UnitSystem, unit_dim: UnitDimension, value: float) -> float:
+    unit_mapping_function = get_map(from_unit, to_unit, unit_dim)
+    if unit_mapping_function is None:
+        return value
+    return unit_mapping_function(value)
+
+
+def convert_object_units(obj: T, to_unit: UnitSystem) -> T:
+    """Inplace conversion of all attributes on the provided object to the new unit system.
+
+    Args:
+        obj (UnitConvertableObject): The object to convert attributes of.
+        to_unit (UnitSystem): The unit system to convert to.
+    """
+    for attr, value in obj.__dict__.items():
+        # TODO: use the typing in the dict rather than checking if it is a float
+        if isinstance(value, float):
+
+            attribute_unit_dims = obj.units.attribute_map.get(attr, None)
+            if attribute_unit_dims is None:
+                continue
+            converted_value = convert_units(obj.unit_system,
+                                            to_unit,
+                                            attribute_unit_dims,
+                                            value)
+            setattr(obj, attr, converted_value)
+    obj._unit_system = to_unit
+    return obj
diff --git a/tests/Units/test_unit_conversion.py b/tests/Units/test_unit_conversion.py
new file mode 100644
index 000000000..da44696a9
--- /dev/null
+++ b/tests/Units/test_unit_conversion.py
@@ -0,0 +1,22 @@
+from ResSimpy.Nexus.DataModels.Network.NexusWellConnection import NexusWellConnection
+from ResSimpy.Nexus.NexusEnums.DateFormatEnum import DateFormat
+from ResSimpy.Units.convert_units import convert_object_units
+from ResSimpy.Enums.UnitsEnum import UnitSystem
+
+
+def test_unit_object_conversion(mocker):
+    # Arrange
+
+    test_obj = NexusWellConnection(
+        properties_dict=dict(diameter=100.1),
+        unit_system=UnitSystem.ENGLISH, date='01/01/2020', date_format=DateFormat.DD_MM_YYYY
+    )
+
+    to_unit = UnitSystem.METBAR
+
+    # Act
+    result = convert_object_units(test_obj, to_unit)
+
+    # Assert
+    assert result.diameter == 100.1 * 2.54
+    assert result.units.unit_system == to_unit