diff --git a/process/models/build.py b/process/models/build.py
index 146002c33c..179a319d3a 100644
--- a/process/models/build.py
+++ b/process/models/build.py
@@ -76,6 +76,34 @@ def run(self):
             dx_beam_shield=self.data.current_drive.dx_beam_shield,
         )
 
+        self.calculate_cs_area()
+
+    def calculate_cs_area(self):
+        """Calculates the CS cross-sectional areas."""
+        # Central Solenoid mean radius
+        r_cs_middle = self.data.build.dr_cs_bore + (0.5e0 * self.data.build.dr_cs)
+
+        # Scale the CS height relative to TF bore height
+        z_cs_half = (
+            self.data.build.z_tf_inside_half * self.data.pf_coil.f_z_cs_tf_internal
+        )
+
+        dz_cs_full = 2.0e0 * z_cs_half  # Full height of CS coil
+
+        # Radius of outer edge
+        r_cs_coil_outer = r_cs_middle + 0.5e0 * self.data.build.dr_cs
+
+        # Radius of inner edge
+        r_cs_coil_inner = r_cs_coil_outer - self.data.build.dr_cs
+
+        # Total poloidal cross-sectional area [m²]
+        self.data.pf_coil.a_cs_poloidal = dz_cs_full * self.data.build.dr_cs
+
+        # Total top-down toroidal cross-sectional area [m²]
+        self.data.pf_coil.a_cs_toroidal = np.pi * (
+            r_cs_coil_outer**2 - r_cs_coil_inner**2
+        )
+
     @staticmethod
     def calculate_beam_port_size(
         f_radius_beam_tangency_rmajor: float,
diff --git a/process/models/pfcoil.py b/process/models/pfcoil.py
index e8d02c8b27..c8bf6b0a4d 100644
--- a/process/models/pfcoil.py
+++ b/process/models/pfcoil.py
@@ -194,8 +194,6 @@ def pfcoil(self):
         self.data.pf_coil.r_cs_inner = self.data.pf_coil.r_pf_coil_inner[
             self.data.pf_coil.n_cs_pf_coils - 1
         ] = cs_geometry.r_cs_coil_inner
-        self.data.pf_coil.a_cs_poloidal = cs_geometry.a_cs_poloidal
-        self.data.pf_coil.a_cs_toroidal = cs_geometry.a_cs_toroidal
         self.data.pf_coil.dz_cs_full = cs_geometry.dz_cs_full
         self.data.pf_coil.dr_cs_full = cs_geometry.dr_cs_full
 
@@ -3073,10 +3071,6 @@ class CSGeometry:
     """Outer radius of CS coil (m)"""
     r_cs_coil_inner: float
     """Inner radius of CS coil (m)"""
-    a_cs_poloidal: float
-    """Total poloidal cross-sectional area of CS coil (m²)"""
-    a_cs_toroidal: float
-    """Total top-down toroidal cross-sectional area of CS coil (m²)"""
     dz_cs_full: float
     """Full height of CS coil (m)"""
     dr_cs_full: float
@@ -3166,12 +3160,6 @@ def calculate_cs_geometry(
         # Full radial thickness of CS coil
         dr_cs_full = 2 * r_cs_coil_outer
 
-        # Total poloidal cross-sectional area [m²]
-        a_cs_poloidal = dz_cs_full * dr_cs
-
-        # Total top-down toroidal cross-sectional area [m²]
-        a_cs_toroidal = np.pi * (r_cs_coil_outer**2 - r_cs_coil_inner**2)
-
         return CSGeometry(
             z_cs_coil_upper=z_cs_coil_upper,
             z_cs_coil_lower=z_cs_coil_lower,
@@ -3180,8 +3168,6 @@ def calculate_cs_geometry(
             z_cs_coil_middle=z_cs_coil_middle,
             r_cs_coil_outer=r_cs_coil_outer,
             r_cs_coil_inner=r_cs_coil_inner,
-            a_cs_poloidal=a_cs_poloidal,
-            a_cs_toroidal=a_cs_toroidal,
             dz_cs_full=dz_cs_full,
             dr_cs_full=dr_cs_full,
         )
@@ -3368,8 +3354,6 @@ def ohcalc(self):
         self.data.pf_coil.r_cs_inner = self.data.pf_coil.r_pf_coil_inner[
             self.data.pf_coil.n_cs_pf_coils - 1
         ] = cs_geometry.r_cs_coil_inner
-        self.data.pf_coil.a_cs_poloidal = cs_geometry.a_cs_poloidal
-        self.data.pf_coil.a_cs_toroidal = cs_geometry.a_cs_toroidal
         self.data.pf_coil.dz_cs_full = cs_geometry.dz_cs_full
         self.data.pf_coil.dr_cs_full = cs_geometry.dr_cs_full
 
diff --git a/tests/unit/models/test_pfcoil.py b/tests/unit/models/test_pfcoil.py
index a7b8c4fe64..80144eea60 100644
--- a/tests/unit/models/test_pfcoil.py
+++ b/tests/unit/models/test_pfcoil.py
@@ -2064,8 +2064,6 @@ def test_brookscoil(pfcoil):
                 0.0,
                 0.44999999999999996,
                 0.14999999999999997,
-                0.6,
-                0.5654866776461627,
                 2.0,
                 0.8999999999999999,
             ),
@@ -2076,7 +2074,7 @@ def test_brookscoil(pfcoil):
             0.5,
             0.0,
             0.0,
-            CSGeometry(1.0, -1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 2.0, 0.0),
+            CSGeometry(1.0, -1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 2.0, 0.0),
         ),
         # Zero fractional height
         (
@@ -2093,8 +2091,6 @@ def test_brookscoil(pfcoil):
                 1.7999999999999998,
                 1.4999999999999998,
                 0.0,
-                3.1101767270538945,
-                0.0,
                 3.5999999999999996,
             ),
         ),
@@ -2727,6 +2723,8 @@ class OhCalcParam(NamedTuple):
     rmajor: Any = None
     plasma_current: Any = None
     poisson_steel: Any = None
+    a_cs_poloidal: float = None
+    a_cs_toroidal: float = None
     exp_b_pf_coil_peak: Any = None
     exp_j_cs_critical_flat_top_end: Any = None
 
@@ -2778,6 +2776,8 @@ class OhCalcParam(NamedTuple):
             rmajor=8.938,
             plasma_current=1.8254e7,
             poisson_steel=3.0e-1,
+            a_cs_poloidal=10.3868352,
+            a_cs_toroidal=12.2710609,
             exp_b_pf_coil_peak=13.073958753751993,
             exp_j_cs_critical_flat_top_end=54101481.7685945,
         )
@@ -2834,6 +2834,8 @@ def test_ohcalc(monkeypatch, reinitialise_error_module, cs_coil, ohcalcparam):
         "c_pf_cs_coil_pulse_start_ma",
         "c_pf_cs_coil_flat_top_ma",
         "c_pf_cs_coil_pulse_end_ma",
+        "a_cs_toroidal",
+        "a_cs_poloidal",
     ]:
         monkeypatch.setattr(cs_coil.data.pf_coil, field, getattr(ohcalcparam, field))