diff --git a/src/com/annimon/ownlang/lib/modules/functions/std_length.java b/src/com/annimon/ownlang/lib/modules/functions/std_length.java
new file mode 100644
index 0000000..b6aa93d
--- /dev/null
+++ b/src/com/annimon/ownlang/lib/modules/functions/std_length.java
@@ -0,0 +1,37 @@
+package com.annimon.ownlang.lib.modules.functions;
+
+import com.annimon.ownlang.lib.*;
+
+public final class std_length implements Function {
+
+    @Override
+    public Value execute(Value... args) {
+        if (args.length == 0) throw new RuntimeException("At least one arg expected");
+        
+        final Value val = args[0];
+        int length;
+        switch (val.type()) {
+            case Types.ARRAY:
+                length = ((ArrayValue) val).size();
+                break;
+            case Types.MAP:
+                length = ((MapValue) val).size();
+                break;
+            case Types.STRING:
+                length = ((StringValue) val).length();
+                break;
+            case Types.FUNCTION:
+                final Function func = ((FunctionValue) val).getValue();
+                if (func instanceof UserDefinedFunction) {
+                    length = ((UserDefinedFunction) func).getArgsCount();
+                } else {
+                    length = 0;
+                }
+                break;
+            default:
+                length = 0;
+                
+        }
+        return new NumberValue(length);
+    }
+}
\ No newline at end of file
diff --git a/src/com/annimon/ownlang/lib/modules/std.java b/src/com/annimon/ownlang/lib/modules/std.java
index 3919698..d5e7746 100644
--- a/src/com/annimon/ownlang/lib/modules/std.java
+++ b/src/com/annimon/ownlang/lib/modules/std.java
@@ -13,6 +13,7 @@ public final class std implements Module {
     public void init() {
         Functions.set("echo", new std_echo());
         Functions.set("newarray", new std_newarray());
+        Functions.set("length", new std_length());
         Functions.set("rand", new std_rand());
         Functions.set("sleep", new std_sleep());
         Functions.set("thread", new std_thread());