diff --git a/src/builtin/string.rs b/src/builtin/string.rs
index cb4eeb6..2b8ddc6 100644
--- a/src/builtin/string.rs
+++ b/src/builtin/string.rs
@@ -1,7 +1,8 @@
 use std::collections::BTreeMap;
 
 use super::Builtin;
-use crate::value::Value;
+use crate::units::Unit;
+use crate::value::{Number, Value};
 
 pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
     decl!(f "to-upper-case", |args, _| {
@@ -18,4 +19,11 @@ pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
             _ => todo!("")
         }
     });
+    decl!(f "str-length", |args, _| {
+        let s: &Value = arg!(args, 0, "string");
+        match s.eval() {
+            Value::Ident(i, _) => Some(Value::Dimension(Number::from(i.len()), Unit::None)),
+            _ => todo!("")
+        }
+    });
 }
diff --git a/src/value/number.rs b/src/value/number.rs
index 787ce65..5d6d20c 100644
--- a/src/value/number.rs
+++ b/src/value/number.rs
@@ -30,14 +30,22 @@ impl From<BigInt> for Number {
     }
 }
 
-impl From<u16> for Number {
-    fn from(b: u16) -> Self {
-        Number {
-            val: BigRational::from_integer(BigInt::from(b)),
+macro_rules! from_integer {
+    ($ty:ty) => {
+        impl From<$ty> for Number {
+            fn from(b: $ty) -> Self {
+                Number {
+                    val: BigRational::from_integer(BigInt::from(b)),
+                }
+            }
         }
-    }
+    };
 }
 
+from_integer!(u16);
+from_integer!(usize);
+from_integer!(i32);
+
 impl Display for Number {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.val.to_integer())?;
diff --git a/tests/strings.rs b/tests/strings.rs
index 5db0bcd..79f7236 100644
--- a/tests/strings.rs
+++ b/tests/strings.rs
@@ -23,3 +23,13 @@ test!(
     "a {\n  color: to-lower-case($string: AbC123);\n}\n",
     "a {\n  color: abc123;\n}\n"
 );
+test!(
+    length_ident,
+    "a {\n  color: str-length(AbC123);\n}\n",
+    "a {\n  color: 6;\n}\n"
+);
+test!(
+    length_named_arg,
+    "a {\n  color: str-length($string: aBc123);\n}\n",
+    "a {\n  color: 6;\n}\n"
+);
\ No newline at end of file