diff --git a/gdshelpers/helpers/small.py b/gdshelpers/helpers/small.py
index e7f82a7..9196148 100644
--- a/gdshelpers/helpers/small.py
+++ b/gdshelpers/helpers/small.py
@@ -1,6 +1,7 @@
 import string
 import numpy as np
 import numpy.linalg as linalg
+import re
 
 
 def raith_eline_dosefactor_to_datatype(dose_factor):
@@ -47,6 +48,18 @@ def id_to_alphanumeric(column, row):
     return int_to_alphabet(row) + str(int(column))
 
 
+def alphanumeric_to_id(text):
+    """
+    Do the reverse of `id_to_alphanumeric`.
+    :return: (column, row) tuple.
+    """
+    regex = "([A-Z]*)([0-9]*)"
+    m = re.match(regex, text, re.I)
+    letters, number = m.group(1), int(m.group(2))
+    letter_num = sum((ord(letter) - ord('A') + 1) * 26 ** i for i, letter in enumerate(letters[::-1]))
+    return number, letter_num - 1
+
+
 def normalize_phase(phase, zero_to_two_pi=False):
     """
     Normalize a phase to be within +/- pi.
diff --git a/gdshelpers/tests/test_helpers.py b/gdshelpers/tests/test_helpers.py
index 83fe0a3..afbb081 100644
--- a/gdshelpers/tests/test_helpers.py
+++ b/gdshelpers/tests/test_helpers.py
@@ -3,6 +3,7 @@
 import numpy.testing as npt
 
 from gdshelpers.helpers import int_to_alphabet, id_to_alphanumeric, find_line_intersection
+from gdshelpers.helpers.small import alphanumeric_to_id
 
 
 class HelpersTestCase(unittest.TestCase):
@@ -15,6 +16,12 @@ def test_int_to_alphabet(self):
     def test_id_to_alphanumeric(self):
         self.assertEqual(id_to_alphanumeric(4, 26 + 25), 'AZ4')
 
+    def test_alphanumeric_to_id(self):
+        self.assertEqual((4, 26 + 25), alphanumeric_to_id('AZ4'))
+
+        for pair in [(0, 0), (0, 10), (0, 100), (100, 0), (100, 100)]:
+            self.assertEqual(pair, alphanumeric_to_id(id_to_alphanumeric(*pair)))
+
     def test_find_line_intersection(self):
         test_intersection = find_line_intersection(np.array((2, 0)), np.pi / 2, np.array((0, 1)), 0)
         npt.assert_almost_equal(test_intersection[0], (2, 1))