diff --git a/glassure/core/calc.py b/glassure/core/calc.py
index c6113e7..843f582 100644
--- a/glassure/core/calc.py
+++ b/glassure/core/calc.py
@@ -7,6 +7,8 @@
 from .utility import calculate_incoherent_scattering, calculate_f_squared_mean, calculate_f_mean_squared, \
     convert_density_to_atoms_per_cubic_angstrom
 
+from .methods import SqMethod, NormalizationMethod, FourierTransformMethod
+
 __all__ = ['calculate_normalization_factor_raw', 'calculate_normalization_factor', 'fit_normalization_factor',
            'calculate_sq', 'calculate_sq_raw', 'calculate_sq_from_fr', 'calculate_sq_from_gr',
            'calculate_fr', 'calculate_gr_raw', 'calculate_gr']
@@ -139,10 +141,10 @@ def calculate_sq_raw(sample_pattern: Pattern, f_squared_mean: np.ndarray, f_mean
     if incoherent_scattering is None:
         incoherent_scattering = np.zeros_like(q)
 
-    if method == 'FZ':
+    if method == 'FZ' or method == SqMethod.FZ:
         sq = (normalization_factor * intensity - incoherent_scattering - f_squared_mean + f_mean_squared) / \
              f_mean_squared
-    elif method == 'AL':
+    elif method == 'AL' or method == SqMethod.AL:
         sq = (normalization_factor * intensity - incoherent_scattering) / f_squared_mean
     else:
         raise NotImplementedError('{} method is not implemented'.format(method))
@@ -188,7 +190,7 @@ def calculate_sq(sample_pattern: Pattern, density: float, composition: dict[str,
         incoherent_scattering = None
 
     atomic_density = convert_density_to_atoms_per_cubic_angstrom(composition, density)
-    if normalization_method == 'fit':
+    if normalization_method == 'fit' or normalization_method == NormalizationMethod.FIT:
         normalization_factor = fit_normalization_factor(sample_pattern,
                                                         composition,
                                                         use_incoherent_scattering,
@@ -238,9 +240,9 @@ def calculate_fr(sq_pattern: Pattern, r: Optional[np.ndarray] = None, use_modifi
     else:
         modification = 1
 
-    if method == 'integral':
+    if method == 'integral' or method == FourierTransformMethod.INTEGRAL:
         fr = 2.0 / np.pi * np.trapz(modification * q * (sq - 1) * np.array(np.sin(np.outer(q.T, r))).T, q)
-    elif method == 'fft':
+    elif method == 'fft' or method == FourierTransformMethod.FFT:
         q_step = q[1] - q[0]
         r_step = r[1] - r[0]
 
diff --git a/glassure/core/methods.py b/glassure/core/methods.py
new file mode 100644
index 0000000..f2345d2
--- /dev/null
+++ b/glassure/core/methods.py
@@ -0,0 +1,25 @@
+from enum import Enum
+
+
+class SqMethod(Enum):
+    """
+    Enum class for the different methods to calculate the structure factor.
+    """
+    FZ = 'FZ'
+    AL = 'AL'
+
+
+class NormalizationMethod(Enum):
+    """
+    Enum class for the different methods to perform an intensity normalization.
+    """
+    INTEGRAL = 'integral'
+    FIT = 'fit'
+
+
+class FourierTransformMethod(Enum):
+    """
+    Enum class for the different methods to perform a Fourier transform.
+    """
+    FFT = 'fft'
+    INTEGRAL = 'integral'
diff --git a/glassure/gui/model/configuration.py b/glassure/gui/model/configuration.py
index 54ae062..686906d 100644
--- a/glassure/gui/model/configuration.py
+++ b/glassure/gui/model/configuration.py
@@ -1,12 +1,13 @@
 # -*- coding: utf-8 -*/:
 from __future__ import annotations
-from enum import StrEnum
+from enum import Enum
 from colorsys import hsv_to_rgb
 from copy import deepcopy
 
 import numpy as np
 
 from ...core.pattern import Pattern
+from ...core.methods import SqMethod, NormalizationMethod, FourierTransformMethod
 
 
 class TransformConfiguration(object):
@@ -273,30 +274,6 @@ def get_pattern_or_none(pattern_dict):
         return config
 
 
-class SqMethod(StrEnum):
-    """
-    Enum class for the different methods to calculate the structure factor.
-    """
-    FZ = 'FZ'
-    AL = 'AL'
-
-
-class NormalizationMethod(StrEnum):
-    """
-    Enum class for the different methods to perform an intensity normalization.
-    """
-    INTEGRAL = 'integral'
-    FIT = 'fit'
-
-
-class FourierTransformMethod(StrEnum):
-    """
-    Enum class for the different methods to perform a Fourier transform.
-    """
-    FFT = 'fft'
-    INTEGRAL = 'integral'
-
-
 def calculate_color(ind):
     s = 0.8
     v = 0.8
diff --git a/glassure/gui/widgets/control/options.py b/glassure/gui/widgets/control/options.py
index e716002..7ba4d7e 100644
--- a/glassure/gui/widgets/control/options.py
+++ b/glassure/gui/widgets/control/options.py
@@ -3,7 +3,8 @@
 from qtpy import QtCore, QtWidgets
 from ..custom import HorizontalLine, FloatLineEdit, DragSlider
 import numpy as np
-from ...model.configuration import NormalizationMethod, SqMethod, TransformConfiguration, FourierTransformMethod
+from ...model.configuration import TransformConfiguration
+from ....core.methods import SqMethod, NormalizationMethod, FourierTransformMethod
 
 
 class OptionsWidget(QtWidgets.QWidget):
@@ -165,7 +166,7 @@ def get_fourier_transform_method(self):
             return FourierTransformMethod.INTEGRAL
 
     def set_fourier_transform_method(self, method):
-        if method == 'fft':
+        if method == 'fft' or method == FourierTransformMethod.FFT:
             self.fft_cb.setChecked(True)
         else:
             self.fft_cb.setChecked(False)