diff --git a/composer.json b/composer.json
index 62430df..c063b5e 100644
--- a/composer.json
+++ b/composer.json
@@ -12,5 +12,7 @@
             "email": "grumpydeveloper@contentnation.net"
         }
     ],
-    "require": {}
+    "require": {
+        "arokettu/arithmetic-parser": "*"
+    }
 }
diff --git a/scriptedbrowser/commands/base.php b/scriptedbrowser/commands/base.php
index 9501969..1f28468 100644
--- a/scriptedbrowser/commands/base.php
+++ b/scriptedbrowser/commands/base.php
@@ -7,6 +7,28 @@
  **/
 namespace ScriptedBrowser\Commands;
 
+/**
+ * calculate given formula
+ *
+ * @param \ScriptedBrowser\Main $main main instance
+ * @param \ScriptedBrowser\Control $control control interface
+ * @param array<string,mixed>  $options options
+ * @return bool always true
+ */
+function calc($main, $control, $options)
+{
+    require_once 'vendor/autoload.php';
+    $input = $main->vars($options['parameter']);
+    $result = $options['result'];
+    try {
+        $calc = \Arokettu\ArithmeticParser\Calculator::evaluate($input);
+        $main->setVar($result, $calc);
+        return true;
+    } catch (\Exception) {
+        return false;
+    }
+}
+
 /**
  * inject and execute given javascript
  *