diff --git a/netbox/ipam/migrations/0083_vlangroup_populate_total_vlan_ids.py b/netbox/ipam/migrations/0083_vlangroup_populate_total_vlan_ids.py
new file mode 100644
index 00000000000..cdf25a17bd5
--- /dev/null
+++ b/netbox/ipam/migrations/0083_vlangroup_populate_total_vlan_ids.py
@@ -0,0 +1,26 @@
+from django.db import migrations
+
+
+def populate_vlangroup_total_vlan_ids(apps, schema_editor):
+    VLANGroup = apps.get_model('ipam', 'VLANGroup')
+    db = schema_editor.connection.alias
+
+    qs = VLANGroup.objects.using(db).only('id', 'vid_ranges')
+    for group in qs.iterator():
+        total_vlan_ids = 0
+        if group.vid_ranges:
+            for r in group.vid_ranges:
+                # Half-open [lo, hi): length is (hi - lo).
+                if r is not None and r.lower is not None and r.upper is not None:
+                    total_vlan_ids += r.upper - r.lower
+        VLANGroup.objects.using(db).filter(pk=group.pk).update(_total_vlan_ids=total_vlan_ids)
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('ipam', '0082_add_prefix_network_containment_indexes'),
+    ]
+
+    operations = [
+        migrations.RunPython(populate_vlangroup_total_vlan_ids, migrations.RunPython.noop),
+    ]
diff --git a/netbox/ipam/models/vlans.py b/netbox/ipam/models/vlans.py
index efa1ed39ed3..030633330a4 100644
--- a/netbox/ipam/models/vlans.py
+++ b/netbox/ipam/models/vlans.py
@@ -132,7 +132,8 @@ def clean(self):
     def save(self, *args, **kwargs):
         self._total_vlan_ids = 0
         for vid_range in self.vid_ranges:
-            self._total_vlan_ids += vid_range.upper - vid_range.lower + 1
+            # VID range is inclusive on lower-bound, exclusive on upper-bound
+            self._total_vlan_ids += vid_range.upper - vid_range.lower
 
         super().save(*args, **kwargs)
 
diff --git a/netbox/ipam/tests/test_models.py b/netbox/ipam/tests/test_models.py
index 656f62d87c2..c93a47d21fe 100644
--- a/netbox/ipam/tests/test_models.py
+++ b/netbox/ipam/tests/test_models.py
@@ -661,6 +661,10 @@ def test_overlapping_vlan(self):
         vlangroup.full_clean()
         vlangroup.save()
 
+    def test_total_vlan_ids(self):
+        vlangroup = VLANGroup.objects.first()
+        self.assertEqual(vlangroup._total_vlan_ids, 100)
+
 
 class TestVLAN(TestCase):