diff --git a/requirements-dev.txt b/requirements-dev.txt
index bfc4244dd50550b5bb203e12f8d82c36ed520829..e1cb212da86cb0f352db5193bbf87097b2e87414 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -20,3 +20,4 @@ linuxdoc==20211220
 aiounittest==1.4.1
 numexpr==2.8.1
 werkzeug==2.0.3
+wrapt-timeout-decorator==1.3.8
diff --git a/requirements.txt b/requirements.txt
index a91f92fc0c61680b8c947fe5e9d2d5cc67b3991e..31f48c2691c6f5a32ea4825df28b322b897ff31d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -18,3 +18,4 @@ redis==3.4.1
 ring==0.7.3
 numexpr==2.8.1
 werkzeug==2.0.3
+wrapt-timeout-decorator==1.3.8
\ No newline at end of file
diff --git a/searx/plugins/calculator.py b/searx/plugins/calculator.py
index f8a7eefa631fbf3955595d1918fb0288d320b284..c0b5499f6843eeb080ed33c090313408988b43af 100644
--- a/searx/plugins/calculator.py
+++ b/searx/plugins/calculator.py
@@ -1,7 +1,7 @@
 from searx import logger
 from numexpr import evaluate
 from flask_babel import gettext
-
+from wrapt_timeout_decorator import timeout
 
 name = gettext('Calculator')
 description = gettext('This plugin extends results when the query is a mathematical expression')
@@ -13,12 +13,10 @@ def check_if_loaded():
     logger.debug("initializing calculator plugin")
 
 
-def is_really_big(query):
-    # For cases like 2**99999**9999
-    if len(query.split("**")) >= 3:
-        return True
-    # Add more cases if needed
-    return False
+# Set timeout so that the plugin doesn't hang for long computations
+@timeout(5)
+def calculate(query):
+    return evaluate(query).item()
 
 
 def post_search(request, search):
@@ -27,8 +25,11 @@ def post_search(request, search):
     try:
         query = search.search_query.query.lower()
         unmodified_query = query
+
+        # Replace all frequently used substitutes
         query = query.replace("x", "*")
         query = query.replace("^", "**")
+        query = query.replace("%", "*0.01")
 
         # Not going to compute if only one number is present
         try:
@@ -45,18 +46,18 @@ def post_search(request, search):
         if len(query) > 30:
             return
 
-        # Not going to compute the result if the query is not within permissible range
-        if is_really_big(query):
-            raise OverflowError
+        # Multiply by float to upcast all numbers to floats
+        # https://numexpr.readthedocs.io/projects/NumExpr3/en/latest/user_guide.html#casting-rules
+        query += "*1.0"
 
-        value = evaluate(query).item()
+        value = calculate(query)
         if type(value) in (int, float):
             search.result_container.answers.clear()
             answer = "{} = {}".format(unmodified_query, value)
-            search.result_container.answers[answer] = {'answer': answer, 'calculator': True}
-    except (ZeroDivisionError, ValueError, FloatingPointError, MemoryError, OverflowError) as e:
+            search.result_container.answers['calculator'] = {'answer': answer, 'calculator': True}
+    except (ZeroDivisionError, ValueError, FloatingPointError, MemoryError, OverflowError, TimeoutError) as e:
         answer = gettext('Error')
-        search.result_container.answers[answer] = {'answer': answer, 'calculator': True}
+        search.result_container.answers['calculator'] = {'answer': answer, 'calculator': True}
     except Exception as e:
         logger.debug(e)
 
diff --git a/tests/unit/test_plugins.py b/tests/unit/test_plugins.py
index 9ef4cd6927397af525ab6d972ca1d6c759652a54..c4f323c2515d4fa68954425f3c96a85ce56523f9 100644
--- a/tests/unit/test_plugins.py
+++ b/tests/unit/test_plugins.py
@@ -137,3 +137,51 @@ class HashPluginTest(SearxTestCase):
         self.assertTrue('sha512 hash digest: ee26b0dd4af7e749aa1a8ee3c10ae9923f6'
                         '18980772e473f8819a5d4940e0db27ac185f8a0e1d5f84f88bc887fd67b143732c304cc5'
                         'fa9ad8e6f57f50028a8ff' in search.result_container.answers['hash']['answer'])
+
+
+class CalculatorPluginTest(SearxTestCase):
+
+    def test_PluginStore_init(self):
+        store = plugins.PluginStore()
+        store.register(plugins.calculator)
+
+        self.assertTrue(len(store.plugins) == 1)
+
+        request = Mock(remote_addr='127.0.0.1')
+        request.headers.getlist.return_value = []
+
+        # True addition test
+        search = get_search_mock(query='2+2', pageno=1)
+        store.call(store.plugins, 'post_search', request, search)
+        self.assertTrue('4'
+                        in search.result_container.answers['calculator']['answer'])
+
+        # False addition test
+        search = get_search_mock(query='2+2', pageno=1)
+        store.call(store.plugins, 'post_search', request, search)
+        self.assertFalse('4' not
+                         in search.result_container.answers['calculator']['answer'])
+
+        # no result test
+        search = get_search_mock(query='2+2', pageno=2)
+        store.call(store.plugins, 'post_search', request, search)
+        self.assertFalse('calculator'
+                         in search.result_container.answers)
+
+        # no result test
+        search = get_search_mock(query='2+2/sdf', pageno=1)
+        store.call(store.plugins, 'post_search', request, search)
+        self.assertFalse('calculator'
+                         in search.result_container.answers)
+
+        # error result test
+        search = get_search_mock(query='2+2/0', pageno=1)
+        store.call(store.plugins, 'post_search', request, search)
+        self.assertTrue('Error'
+                        in search.result_container.answers['calculator']['answer'])
+
+        # error result test
+        search = get_search_mock(query='2**999999999**99999999', pageno=1)
+        store.call(store.plugins, 'post_search', request, search)
+        self.assertTrue('Error'
+                        in search.result_container.answers['calculator']['answer'])