diff --git a/src/builtin/functions/meta.rs b/src/builtin/functions/meta.rs
index d6e3fd9..7ad6e34 100644
--- a/src/builtin/functions/meta.rs
+++ b/src/builtin/functions/meta.rs
@@ -7,7 +7,6 @@ use crate::{
     common::{Identifier, QuoteKind},
     error::SassResult,
     parse::Parser,
-    unit::Unit,
     value::{SassFunction, Value},
 };
 
@@ -73,12 +72,7 @@ pub(crate) fn type_of(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult
 
 pub(crate) fn unitless(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult<Value> {
     args.max_args(1)?;
-    #[allow(clippy::match_same_arms)]
-    Ok(match args.get_err(0, "number")? {
-        Value::Dimension(_, Unit::None, _) => Value::True,
-        Value::Dimension(..) => Value::False,
-        _ => Value::True,
-    })
+    Ok(Value::bool(args.get_err(0, "number")?.unitless()))
 }
 
 pub(crate) fn inspect(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult<Value> {
diff --git a/src/builtin/modules/math.rs b/src/builtin/modules/math.rs
index 36f8019..533f6e9 100644
--- a/src/builtin/modules/math.rs
+++ b/src/builtin/modules/math.rs
@@ -1,3 +1,5 @@
+use std::cmp::Ordering;
+
 use crate::{
     args::CallArgs,
     builtin::{
@@ -5,6 +7,7 @@ use crate::{
         meta::{unit, unitless},
         modules::Module,
     },
+    common::Op,
     error::SassResult,
     parse::Parser,
     unit::Unit,
@@ -16,7 +19,84 @@ use crate::builtin::math::random;
 
 fn clamp(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult<Value> {
     args.max_args(3)?;
-    todo!()
+    let span = args.span();
+
+    let min = match args.get_err(0, "min")? {
+        v @ Value::Dimension(..) => v,
+        v => {
+            return Err((
+                format!("$min: {} is not a number.", v.inspect(args.span())?),
+                span,
+            )
+                .into())
+        }
+    };
+
+    let number = match args.get_err(1, "number")? {
+        v @ Value::Dimension(..) => v,
+        v => {
+            return Err((
+                format!("$number: {} is not a number.", v.inspect(span)?),
+                span,
+            )
+                .into())
+        }
+    };
+
+    let max = match args.get_err(2, "max")? {
+        v @ Value::Dimension(..) => v,
+        v => return Err((format!("$max: {} is not a number.", v.inspect(span)?), span).into()),
+    };
+
+    // ensure that `min` and `max` are compatible
+    min.cmp(&max, span, Op::LessThan)?;
+
+    let min_unit = match min {
+        Value::Dimension(_, ref u, _) => u,
+        _ => unreachable!(),
+    };
+    let number_unit = match number {
+        Value::Dimension(_, ref u, _) => u,
+        _ => unreachable!(),
+    };
+    let max_unit = match max {
+        Value::Dimension(_, ref u, _) => u,
+        _ => unreachable!(),
+    };
+
+    if min_unit == &Unit::None && number_unit != &Unit::None {
+        return Err((
+            format!(
+                "$min is unitless but $number has unit {}. Arguments must all have units or all be unitless.",
+                number_unit
+            ), span).into());
+    } else if min_unit != &Unit::None && number_unit == &Unit::None {
+        return Err((
+                format!(
+                    "$min has unit {} but $number is unitless. Arguments must all have units or all be unitless.",
+                    min_unit
+                ), span).into());
+    } else if min_unit != &Unit::None && max_unit == &Unit::None {
+        return Err((
+            format!(
+                "$min has unit {} but $max is unitless. Arguments must all have units or all be unitless.",
+                min_unit
+            ), span).into());
+    }
+
+    match min.cmp(&number, span, Op::LessThan)? {
+        Ordering::Greater => return Ok(min),
+        Ordering::Equal => return Ok(number),
+        Ordering::Less => {}
+    }
+
+    match max.cmp(&number, span, Op::GreaterThan)? {
+        Ordering::Less => return Ok(max),
+        Ordering::Equal => return Ok(number),
+        Ordering::Greater => {}
+    }
+
+    Ok(number)
 }
 
 fn hypot(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult<Value> {
@@ -84,6 +164,7 @@ pub(crate) fn declare(f: &mut Module) {
     f.insert_builtin("is-unitless", unitless);
     f.insert_builtin("unit", unit);
     f.insert_builtin("percentage", percentage);
+    f.insert_builtin("clamp", clamp);
     #[cfg(feature = "random")]
     f.insert_builtin("random", random);
 
diff --git a/src/parse/value/eval.rs b/src/parse/value/eval.rs
index 94c5101..736eed9 100644
--- a/src/parse/value/eval.rs
+++ b/src/parse/value/eval.rs
@@ -735,53 +735,9 @@ impl<'a, 'b: 'a> ValueVisitor<'a, 'b> {
             HigherIntermediateValue::Literal(v) => v,
             v => panic!("{:?}", v),
         };
-        let ordering = match left {
-            Value::Dimension(num, unit, _) => match &right {
-                Value::Dimension(num2, unit2, _) => {
-                    if !unit.comparable(unit2) {
-                        return Err((
-                            format!("Incompatible units {} and {}.", unit2, unit),
-                            self.span,
-                        )
-                            .into());
-                    }
-                    if &unit == unit2 || unit == Unit::None || unit2 == &Unit::None {
-                        num.cmp(num2)
-                    } else {
-                        num.cmp(
-                            &(num2.clone()
-                                * UNIT_CONVERSION_TABLE[unit.to_string().as_str()]
-                                    [unit2.to_string().as_str()]
-                                .clone()),
-                        )
-                    }
-                }
-                v => {
-                    return Err((
-                        format!(
-                            "Undefined operation \"{} {} {}\".",
-                            v.inspect(self.span)?,
-                            op,
-                            right.inspect(self.span)?
-                        ),
-                        self.span,
-                    )
-                        .into())
-                }
-            },
-            _ => {
-                return Err((
-                    format!(
-                        "Undefined operation \"{} {} {}\".",
-                        left.inspect(self.span)?,
-                        op,
-                        right.inspect(self.span)?
-                    ),
-                    self.span,
-                )
-                    .into())
-            }
-        };
+
+        let ordering = left.cmp(&right, self.span, op)?;
+
         Ok(match op {
             Op::GreaterThan => match ordering {
                 Ordering::Greater => Value::True,
diff --git a/src/value/mod.rs b/src/value/mod.rs
index 5cf7cd4..7766b3f 100644
--- a/src/value/mod.rs
+++ b/src/value/mod.rs
@@ -1,10 +1,12 @@
+use std::cmp::Ordering;
+
 use peekmore::PeekMore;
 
 use codemap::{Span, Spanned};
 
 use crate::{
     color::Color,
-    common::{Brackets, ListSeparator, QuoteKind},
+    common::{Brackets, ListSeparator, Op, QuoteKind},
     error::SassResult,
     parse::Parser,
     selector::Selector,
@@ -322,6 +324,63 @@ impl Value {
         }
     }
 
+    pub fn cmp(&self, other: &Self, span: Span, op: Op) -> SassResult<Ordering> {
+        Ok(match self {
+            Value::Dimension(num, unit, _) => match &other {
+                Value::Dimension(num2, unit2, _) => {
+                    if !unit.comparable(unit2) {
+                        return Err(
+                            (format!("Incompatible units {} and {}.", unit2, unit), span).into(),
+                        );
+                    }
+                    if unit == unit2 || unit == &Unit::None || unit2 == &Unit::None {
+                        num.cmp(num2)
+                    } else {
+                        num.cmp(
+                            &(num2.clone()
+                                * UNIT_CONVERSION_TABLE[unit.to_string().as_str()]
+                                    [unit2.to_string().as_str()]
+                                .clone()),
+                        )
+                    }
+                }
+                v => {
+                    return Err((
+                        format!(
+                            "Undefined operation \"{} {} {}\".",
+                            v.inspect(span)?,
+                            op,
+                            other.inspect(span)?
+                        ),
+                        span,
+                    )
+                        .into())
+                }
+            },
+            _ => {
+                return Err((
+                    format!(
+                        "Undefined operation \"{} {} {}\".",
+                        self.inspect(span)?,
+                        op,
+                        other.inspect(span)?
+                    ),
+                    span,
+                )
+                    .into())
+            }
+        })
+    }
+
+    pub fn unitless(&self) -> bool {
+        #[allow(clippy::match_same_arms)]
+        match self {
+            Value::Dimension(_, Unit::None, _) => true,
+            Value::Dimension(..) => false,
+            _ => true,
+        }
+    }
+
     pub fn not_equals(&self, other: &Self) -> bool {
         match self {
             Value::String(s1, ..) => match other {
diff --git a/src/value/number/mod.rs b/src/value/number/mod.rs
index 00152b5..9cbb4ed 100644
--- a/src/value/number/mod.rs
+++ b/src/value/number/mod.rs
@@ -16,7 +16,7 @@ mod integer;
 
 const PRECISION: usize = 10;
 
-#[derive(Clone, Eq, PartialEq, Ord)]
+#[derive(Clone, Eq, PartialEq)]
 pub(crate) enum Number {
     Small(Rational64),
     Big(Box<BigRational>),
@@ -321,6 +321,30 @@ impl PartialOrd for Number {
     }
 }
 
+impl Ord for Number {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match self {
+            Self::Small(val1) => match other {
+                Self::Small(val2) => val1.cmp(val2),
+                Self::Big(val2) => {
+                    let tuple: (i64, i64) = (*val1).into();
+                    BigRational::new_raw(BigInt::from(tuple.0), BigInt::from(tuple.1)).cmp(val2)
+                }
+            },
+            Self::Big(val1) => match other {
+                Self::Small(val2) => {
+                    let tuple: (i64, i64) = (*val2).into();
+                    (**val1).cmp(&BigRational::new_raw(
+                        BigInt::from(tuple.0),
+                        BigInt::from(tuple.1),
+                    ))
+                }
+                Self::Big(val2) => val1.cmp(val2),
+            },
+        }
+    }
+}
+
 impl Add for Number {
     type Output = Self;
 
diff --git a/tests/math-module.rs b/tests/math-module.rs
new file mode 100644
index 0000000..50030df
--- /dev/null
+++ b/tests/math-module.rs
@@ -0,0 +1,40 @@
+#![cfg(test)]
+
+#[macro_use]
+mod macros;
+
+test!(
+    clamp_in_the_middle,
+    "@use 'sass:math';\na {\n  color: math.clamp(0, 1, 2);\n}\n",
+    "a {\n  color: 1;\n}\n"
+);
+test!(
+    clamp_first_is_bigger,
+    "@use 'sass:math';\na {\n  color: math.clamp(2, 1, 0);\n}\n",
+    "a {\n  color: 2;\n}\n"
+);
+test!(
+    clamp_all_same_unit,
+    "@use 'sass:math';\na {\n  color: math.clamp(0px, 1px, 2px);\n}\n",
+    "a {\n  color: 1px;\n}\n"
+);
+test!(
+    clamp_all_different_but_compatible_unit,
+    "@use 'sass:math';\na {\n  color: math.clamp(0mm, 1cm, 2in);\n}\n",
+    "a {\n  color: 1cm;\n}\n"
+);
+error!(
+    clamp_only_min_has_no_unit,
+    "@use 'sass:math';\na {\n  color: math.clamp(0, 1cm, 2in);\n}\n",
+    "Error: $min is unitless but $number has unit cm. Arguments must all have units or all be unitless."
+);
+error!(
+    clamp_only_number_has_no_unit,
+    "@use 'sass:math';\na {\n  color: math.clamp(0mm, 1, 2in);\n}\n",
+    "Error: $min has unit mm but $number is unitless. Arguments must all have units or all be unitless."
+);
+error!(
+    clamp_only_max_has_no_unit,
+    "@use 'sass:math';\na {\n  color: math.clamp(0mm, 1cm, 2);\n}\n",
+    "Error: $min has unit mm but $max is unitless. Arguments must all have units or all be unitless."
+);
diff --git a/tests/ordering.rs b/tests/ordering.rs
index ae00b88..5a2b644 100644
--- a/tests/ordering.rs
+++ b/tests/ordering.rs
@@ -63,3 +63,8 @@ test!(
     "a {\n  color: 0 < 1;\n}\n",
     "a {\n  color: true;\n}\n"
 );
+test!(
+    ord_the_same_as_partial_ord,
+    "a {\n  color: 2in > 1cm;\n}\n",
+    "a {\n  color: true;\n}\n"
+);