diff --git a/rna_tools/tools/PyMOL4RNA/libs/calc_gdt.py b/rna_tools/tools/PyMOL4RNA/libs/calc_gdt.py
new file mode 100644
index 000000000..b1454b32e
--- /dev/null
+++ b/rna_tools/tools/PyMOL4RNA/libs/calc_gdt.py
@@ -0,0 +1,81 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""
+Author: Guillaume Bouvier -- guillaume.bouvier@pasteur.fr
+https://research.pasteur.fr/en/member/guillaume-bouvier/
+2018-01-24 15:23:33 (UTC+0100)
+https://bougui505.github.io/2018/01/24/compute_the_global_distance_test_(gdt)_with_pymol.html
+"""
+
+from pymol import cmd
+import numpy as np
+
+print("Loaded calc_gdt.py: gdt(sel1, sel2), gdt_hs(sel1, sel2)")
+@cmd.extend
+def gdt(sel1, sel2):
+    """
+    Calculate the GDT (Global Distance Test) between two RNA (using P atoms) selections.
+    Args:
+        sel1 (str): selection string for the protein to compare.
+        sel2 (str): selection string for the reference protein.
+    """
+    # Select only C-alpha atoms
+    sel1 += ' and name P'
+    sel2 += ' and name P'
+    cutoffs = [1.0, 2.0, 4.0, 8.0]
+    # Align without transforming for raw alignment data
+    cmd.align(sel1, sel2, cycles=0, transform=0, object='aln')
+    # Get raw alignment data
+    mapping = cmd.get_raw_alignment('aln')
+    distances = []
+    for pair in mapping:
+        atom1 = '%s and id %d' % (pair[0][0], pair[0][1])
+        atom2 = '%s and id %d' % (pair[1][0], pair[1][1])
+        dist = cmd.get_distance(atom1, atom2)
+        distances.append(dist)
+    distances = np.array(distances)
+    gdts = [(distances <= cutoff).mean() for cutoff in cutoffs]
+    out = np.array(list(zip(cutoffs, gdts))).flatten()
+    print("GDT_%d: %.4f; GDT_%d: %.4f; GDT_%d: %.4f; GDT_%d: %.4f;" % tuple(out))
+    GDT = np.mean(gdts)
+    print("GDT: %.4f" % GDT)
+    # Color by distance
+    cmd.spectrum('b', 'green_yellow_red', sel1)
+    return GDT
+
+@cmd.extend
+def gdt_hs(sel1, sel2):
+    """
+    Calculate the GDT (Global Distance Test) High Accuracy between two RNA (using P atoms) selections.
+    Args:
+        sel1 (str): selection string for the protein to compare.
+        sel2 (str): selection string for the reference protein.
+    """
+    # Select only C-alpha atoms
+    sel1 += ' and name P'
+    sel2 += ' and name P'
+    cutoffs = [0.5, 1, 2, 4]
+    # Align without transforming for raw alignment data
+    cmd.align(sel1, sel2, cycles=0, transform=0, object='aln')
+    # Get raw alignment data
+    mapping = cmd.get_raw_alignment('aln')
+    distances = []
+    for pair in mapping:
+        atom1 = '%s and id %d' % (pair[0][0], pair[0][1])
+        atom2 = '%s and id %d' % (pair[1][0], pair[1][1])
+        dist = cmd.get_distance(atom1, atom2)
+        distances.append(dist)
+    distances = np.array(distances)
+    gdts = [(distances <= cutoff).mean() for cutoff in cutoffs]
+    out = np.array(list(zip(cutoffs, gdts))).flatten()
+    print("GDT_HS%d: %.4f; GDT_%d: %.4f; GDT_%d: %.4f; GDT_%d: %.4f;" % tuple(out))
+    GDT = np.mean(gdts)
+    print("GDT_HS: %.4f" % GDT)
+    # Color by distance
+    cmd.spectrum('b', 'green_yellow_red', sel1)
+    return GDT
+
+if __name__ == '__main__':
+    # Assume the first two objects are the models to compare
+    model1, reference = cmd.get_object_list('all')[:2]
+    gdt_gs(model1, reference)