diff --git a/searx/plugins/calculator.py b/searx/plugins/calculator.py
index aef10c559..d963aa304 100644
--- a/searx/plugins/calculator.py
+++ b/searx/plugins/calculator.py
@@ -7,13 +7,12 @@ import operator
 from multiprocessing import Process, Queue
 
 from flask_babel import gettext
-from searx import settings
 
 from searx.plugins import logger
 
 name = "Basic Calculator"
 description = gettext("Calculate mathematical expressions via the search bar")
-default_on = False
+default_on = True
 
 preference_section = 'general'
 plugin_id = 'calculator'
@@ -81,9 +80,6 @@ def timeout_func(timeout, func, *args, **kwargs):
 
 
 def post_search(_request, search):
-    # don't run on public instances due to possible attack surfaces
-    if settings['server']['public_instance']:
-        return True
 
     # only show the result of the expression on the first page
     if search.search_query.pageno > 1:
@@ -113,7 +109,3 @@ def post_search(_request, search):
     if result != query:
         search.result_container.answers['calculate'] = {'answer': f"{query} = {result}"}
     return True
-
-
-def is_allowed():
-    return not settings['server']['public_instance']
diff --git a/searx/settings.yml b/searx/settings.yml
index a1701d009..8f5a4430e 100644
--- a/searx/settings.yml
+++ b/searx/settings.yml
@@ -219,13 +219,13 @@ outgoing:
 #
 # enabled_plugins:
 #   # these plugins are enabled if nothing is configured ..
+#   - 'Basic Calculator'
 #   - 'Hash plugin'
 #   - 'Self Information'
 #   - 'Tracker URL remover'
 #   - 'Ahmia blacklist'  # activation depends on outgoing.using_tor_proxy
 #   # these plugins are disabled if nothing is configured ..
 #   - 'Hostnames plugin'  # see 'hostnames' configuration below
-#   - 'Basic Calculator'
 #   - 'Open Access DOI rewrite'
 #   - 'Tor check plugin'
 #   # Read the docs before activate: auto-detection of the language could be
diff --git a/searx/templates/simple/preferences.html b/searx/templates/simple/preferences.html
index 0145dcd0f..9dab84fd1 100644
--- a/searx/templates/simple/preferences.html
+++ b/searx/templates/simple/preferences.html
@@ -38,7 +38,7 @@
 
 {%- macro plugin_preferences(section) -%}
 {%- for plugin in plugins -%}
-{%- if plugin.preference_section == section and (plugin.is_allowed() if plugin.is_allowed else True) -%}
+{%- if plugin.preference_section == section -%}
 <fieldset>{{- '' -}}
     <legend>{{ _(plugin.name) }}</legend>{{- '' -}}
     <div class="value">