diff --git a/src/clib/xtg/libxtg.h b/src/clib/xtg/libxtg.h
index 9f8281543..b4a0915cb 100644
--- a/src/clib/xtg/libxtg.h
+++ b/src/clib/xtg/libxtg.h
@@ -178,8 +178,6 @@ double
 x_avg_angles(double *swig_np_dbl_in_v1,  // *angles
              long n_swig_np_dbl_in_v1);  // nsize,
 
-double
-x_rotation_conv(double ain, int aimode, int mode, int option);
 
 double
 x_tetrahedron_volume(double *swig_np_dbl_inplaceflat_v1,
diff --git a/src/clib/xtg/x_rotation_conv.c b/src/clib/xtg/x_rotation_conv.c
deleted file mode 100644
index 8162c4ea1..000000000
--- a/src/clib/xtg/x_rotation_conv.c
+++ /dev/null
@@ -1,101 +0,0 @@
-/*
- ******************************************************************************
- *
- * NAME:
- *    x_rotation_convert.c
- *
- *
- * DESCRIPTION:
- *    Transforms different rotation schemes. Ie. to transform from radians
- *    azimuth to degrees anticlock from x:
- *    deg = z_rotation_conv(0.343, 3, 0, 0, 1)
- *
- * ARGUMENTS:
- *    ain            i     Input angle
- *    ainmode        i     Input angle mode:
- *                               0 degrees, anti-clock from X
- *                               1 radians, anti-clock from X
- *                               2 degrees, clock from Y (azimuth)
- *                               3 radians, clock from Y (azimuth)
- *    mode           i     Mode of returning angle (same codes as ainmode)
- *    option         i     Options flag for later usage
- *
- * RETURNS:
- *    Transformed angle.
- *
- * TODO/ISSUES/BUGS:
- *    UNFINISHED! All combinations of conversion are not finished yet
- *
- * LICENCE:
- *    cf. XTGeo LICENSE
- ******************************************************************************
- */
-#include "libxtg.h"
-#include "libxtg_.h"
-
-double
-x_rotation_conv(double ain, int ainmode, int mode, int option)
-{
-    /* locals */
-    double result = 0.0;
-
-    /*
-     * ------------------------------------------------------------------------
-     * Some checks
-     * ------------------------------------------------------------------------
-     */
-
-    if (ainmode == 0 || ainmode == 2) {
-        if (ain < -360 || ain > 360) {
-            return -9;
-        }
-    }
-
-    if (ainmode == 1 || ainmode == 3) {
-        if (ain < -2 * PI || ain > 2 * PI) {
-            return -9;
-        }
-    }
-
-    /*
-     * ------------------------------------------------------------------------
-     * Use degrees when comptuting
-     * ------------------------------------------------------------------------
-     */
-    if (ainmode == 1 || ainmode == 3)
-        ain = ain * 180.0 / PI;
-
-    /*
-     * ------------------------------------------------------------------------
-     * Compute
-     * ------------------------------------------------------------------------
-     */
-
-    /* from angle to azimuth */
-    if (ainmode <= 1 && mode >= 2) {
-        result = -ain + 90;
-        if (result > 360)
-            result = result - 360;
-        if (ainmode == 1)
-            result = result * PI / 180.0;
-    }
-
-    /* convert degrees azimuth angle to degrees normal angle */
-    if (ainmode >= 2 && mode <= 1) {
-        result = 450 - ain;
-        if (result > 360)
-            result = result - 360;
-        if (ainmode == 3)
-            result = result * PI / 180.0;
-    }
-
-    /* convert radians azimuth angle to degrees normal angle */
-    if (ainmode == 3 && mode == 0) {
-        ain = ain * 180 / PI;
-        result = 450 - ain;
-        if (result > 360)
-            result = result - 360;
-    }
-
-    return result;
-}
diff --git a/src/xtgeo/common/_angles.py b/src/xtgeo/common/_angles.py
new file mode 100644
index 000000000..1e59c231d
--- /dev/null
+++ b/src/xtgeo/common/_angles.py
@@ -0,0 +1,29 @@
+from math import degrees, radians
+
+
+def _deg_angle2azimuth(deg: float) -> float:
+    """Converts an angle from X-axis anti-clockwise orientation
+    to Y-axis clockwise azimuth.
+    """
+    return (-deg + 90) % 360
+
+
+def _deg_azimuth2angle(deg: float) -> float:
+    """Converts azimuth from Y-axis clockwise orientation to X-axis
+    anti-clockwise angle.
+    """
+    return (450 - deg) % 360
+
+
+def _rad_angle2azimuth(rad: float) -> float:
+    """Converts an angle from X-axis anti-clockwise orientation to Y-axis clockwise
+    azimuth in radians.
+    """
+    return radians(_deg_angle2azimuth(degrees(rad)))
+
+
+def _rad_azimuth2angle(deg: float) -> float:
+    """Converts azimuth from Y-axis clockwise orientation to X-axis anti-clockwise
+    angle in radians.
+    """
+    return radians(_deg_azimuth2angle(degrees(deg)))
diff --git a/src/xtgeo/common/calc.py b/src/xtgeo/common/calc.py
index 7b91fc96f..5fb9262f4 100644
--- a/src/xtgeo/common/calc.py
+++ b/src/xtgeo/common/calc.py
@@ -8,7 +8,7 @@
 import numpy as np
 
 from xtgeo import XTGeoCLibError, _cxtgeo
-from xtgeo.common import XTGeoDialog, null_logger
+from xtgeo.common import XTGeoDialog, _angles, null_logger
 
 xtg = XTGeoDialog()
 logger = null_logger(__name__)
@@ -207,13 +207,11 @@ def angle2azimuth(
     Return:
         Azimuth angle (in degrees or radian)
     """
-    nmode1 = 0
-    nmode2 = 2
-    if mode == "radians":
-        nmode1 += 1
-        nmode2 += 1
-
-    return _cxtgeo.x_rotation_conv(inangle, nmode1, nmode2, 0)
+    return (
+        _angles._deg_angle2azimuth(inangle)
+        if mode == "degrees"
+        else _angles._rad_angle2azimuth(inangle)
+    )
 
 
 def azimuth2angle(
@@ -232,13 +230,11 @@ def azimuth2angle(
     Return:
         Angle (in degrees or radians)
     """
-    nmode1 = 2
-    nmode2 = 0
-    if mode == "radians":
-        nmode1 += 1
-        nmode2 += 1
-
-    return _cxtgeo.x_rotation_conv(inangle, nmode1, nmode2, 0)
+    return (
+        _angles._deg_azimuth2angle(inangle)
+        if mode == "degrees"
+        else _angles._rad_azimuth2angle(inangle)
+    )
 
 
 def tetrehedron_volume(vertices: Sequence[float]) -> float:
diff --git a/tests/test_common/test_calc.py b/tests/test_common/test_calc.py
index fd804bccf..2506c28fd 100644
--- a/tests/test_common/test_calc.py
+++ b/tests/test_common/test_calc.py
@@ -4,6 +4,8 @@
 
 import numpy as np
 import pytest
+from hypothesis import given
+from hypothesis import strategies as st
 
 import xtgeo
 import xtgeo.common.calc as xcalc
@@ -190,6 +192,36 @@ def test_azimuth2angle():
     assert res == 120
 
 
+@given(
+    x=st.floats(
+        min_value=0,
+        max_value=180,
+        allow_infinity=False,
+        allow_nan=False,
+    )
+)
+def test_angle2azimuth_azimuth2angle_deg(x: float) -> None:
+    assert (
+        pytest.approx(xcalc.azimuth2angle(xcalc.angle2azimuth(x, "degrees"), "degrees"))
+        == x
+    )
+
+
+@given(
+    x=st.floats(
+        min_value=0,
+        max_value=math.pi,
+        allow_infinity=False,
+        allow_nan=False,
+    )
+)
+def test_angle2azimuth_azimuth2angle_rad(x: float) -> None:
+    assert (
+        pytest.approx(xcalc.azimuth2angle(xcalc.angle2azimuth(x, "radians"), "radians"))
+        == x
+    )
+
+
 def test_averageangle():
     """Test finding an average angle"""