diff --git a/pillar/api/utils/__init__.py b/pillar/api/utils/__init__.py
index c244ba63..47225f75 100644
--- a/pillar/api/utils/__init__.py
+++ b/pillar/api/utils/__init__.py
@@ -63,7 +63,7 @@ def remove_private_keys(document):
     return doc_copy
 
 
-def pretty_duration(seconds):
+def pretty_duration(seconds: typing.Union[None, int, float]):
     if seconds is None:
         return ''
     seconds = round(seconds)
@@ -75,6 +75,27 @@ def pretty_duration(seconds):
         return f'{minutes:02}:{seconds:02}'
 
 
+def pretty_duration_fractional(seconds: typing.Union[None, int, float]):
+    if seconds is None:
+        return ''
+
+    # Remove fraction of seconds from the seconds so that the rest is done as integers.
+    seconds, fracs = divmod(seconds, 1)
+    hours, seconds = divmod(int(seconds), 3600)
+    minutes, seconds = divmod(seconds, 60)
+    msec = int(round(fracs * 1000))
+
+    if msec == 0:
+        msec_str = ''
+    else:
+        msec_str = f'.{msec:03}'
+
+    if hours > 0:
+        return f'{hours:02}:{minutes:02}:{seconds:02}{msec_str}'
+    else:
+        return f'{minutes:02}:{seconds:02}{msec_str}'
+
+
 class PillarJSONEncoder(json.JSONEncoder):
     """JSON encoder with support for Pillar resources."""
 
diff --git a/pillar/web/jinja.py b/pillar/web/jinja.py
index 4677d737..57327cac 100644
--- a/pillar/web/jinja.py
+++ b/pillar/web/jinja.py
@@ -35,6 +35,10 @@ def format_pretty_duration(s):
     return pretty_duration(s)
 
 
+def format_pretty_duration_fractional(s):
+    return pillar.api.utils.pretty_duration_fractional(s)
+
+
 def format_undertitle(s):
     """Underscore-replacing title filter.
 
@@ -232,6 +236,7 @@ def setup_jinja_env(jinja_env, app_config: dict):
     jinja_env.filters['pretty_date'] = format_pretty_date
     jinja_env.filters['pretty_date_time'] = format_pretty_date_time
     jinja_env.filters['pretty_duration'] = format_pretty_duration
+    jinja_env.filters['pretty_duration_fractional'] = format_pretty_duration_fractional
     jinja_env.filters['undertitle'] = format_undertitle
     jinja_env.filters['hide_none'] = do_hide_none
     jinja_env.filters['pluralize'] = do_pluralize
diff --git a/tests/test_web/test_jinja.py b/tests/test_web/test_jinja.py
index 7b2b7944..4dc7e56b 100644
--- a/tests/test_web/test_jinja.py
+++ b/tests/test_web/test_jinja.py
@@ -41,3 +41,12 @@ class MarkdownTest(unittest.TestCase):
             '<h1>Title</h1>\n<p>Before</p>\n'
             '<dl><dt>test</dt><dt>a</dt><dd>b</dd><dt>c</dt><dd>d</dd></dl>\n',
             jinja.do_markdowned({'eek': '# Title\n\nBefore\n{test a="b" c="d"}'}, 'eek'))
+
+    def test_pretty_duration_fractional(self):
+        from pillar.web import jinja
+
+        self.assertEqual('03:04.568', jinja.format_pretty_duration_fractional(184.5678911111))
+        self.assertEqual('02:03:04.568', jinja.format_pretty_duration_fractional(7384.5678911111))
+
+        self.assertEqual('03:04', jinja.format_pretty_duration_fractional(184.00049))
+        self.assertEqual('02:03:04', jinja.format_pretty_duration_fractional(7384.00049))