diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index 1622165..0ba96b4 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -93,31 +93,30 @@ impl PreToken {
 				let c = match &s[..] {
 					// Mathematical constants
 					// 100 digits of each.
-					"π"|"pi" => { Some(Token::Constant(Quantity::new_float_from_string(
+					"π"|"pi" => { Some((Quantity::new_float_from_string(
 						"3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067"
 					).unwrap(), String::from("π")))},
 
-					"e" => { Some(Token::Constant(Quantity::new_float_from_string(
+					"e" => { Some((Quantity::new_float_from_string(
 						"2.718281828459045235360287471352662497757247093699959574966967627724076630353547594571382178525166427"
 					).unwrap(), String::from("e"))) },
 
-					"phi"|"φ" => { Some(Token::Constant(Quantity::new_float_from_string(
+					"phi"|"φ" => { Some((Quantity::new_float_from_string(
 						"1.618033988749894848204586834365638117720309179805762862135448622705260462818902449707207204189391137"
 					).unwrap(), String::from("φ"))) },
 
 					_ => { None }
 				};
 
-				if c.is_some() { return Ok(c.unwrap()); }
-
-				let c = Unit::from_string(&s);
-
 				if c.is_some() {
-					let mut q = Quantity::new_rational(1f64).unwrap();
-					q.set_unit(c.unwrap());
-					return Ok(Token::Number(q));
+					let (a, b) = c.unwrap();
+					return Ok(Token::Constant(a, b));
 				}
 
+				let c = Quantity::from_unit_string(&s);
+
+				if c.is_some() { return Ok(Token::Number(c.unwrap())); }
+
 				return Err((l, ParserError::Undefined(s)));
 			}
 
diff --git a/src/quantity/mod.rs b/src/quantity/mod.rs
index f1c149f..c962230 100644
--- a/src/quantity/mod.rs
+++ b/src/quantity/mod.rs
@@ -22,6 +22,11 @@ pub(in crate::quantity) use crate::quantity::scalar::Scalar;
 mod unit;
 pub use crate::quantity::unit::Unit;
 pub use crate::quantity::unit::BaseUnit;
+pub(in crate::quantity) use crate::quantity::unit::CompoundUnit;
 
 mod quantity;
 pub use crate::quantity::quantity::Quantity;
+
+
+
+
diff --git a/src/quantity/quantity.rs b/src/quantity/quantity.rs
index 7bf2779..233afff 100644
--- a/src/quantity/quantity.rs
+++ b/src/quantity/quantity.rs
@@ -7,9 +7,9 @@ use std::ops::{
 };
 use std::cmp::Ordering;
 
-
 use crate::quantity::Unit;
 use crate::quantity::BaseUnit;
+use crate::quantity::CompoundUnit;
 
 
 use crate::quantity::Scalar;
@@ -44,8 +44,6 @@ impl Quantity {
 		return format!("{n} {u}");
 	}
 
-
-
 	pub fn new_float(f: f64) -> Option<Quantity> {
 		let v = Scalar::new_float(f);
 		if v.is_none() { return None; }
@@ -88,6 +86,48 @@ impl Quantity {
 
 	pub fn insert_unit(&mut self, ui: BaseUnit, pi: f64) { self.u.insert(ui, pi) }
 	pub fn set_unit(&mut self, u: Unit) { self.u = u; }
+
+	pub fn from_unit_string(s: &str) -> Option<Quantity> {
+		// Base Units
+		let b = match s {
+			"m" => Some(BaseUnit::Meter),
+			"s" => Some(BaseUnit::Second),
+			"kg" => Some(BaseUnit::Kilogram),
+			"a" => Some(BaseUnit::Ampere),
+			"k" => Some(BaseUnit::Kelvin),
+			"mol" => Some(BaseUnit::Mole),
+			"c" => Some(BaseUnit::Candela),
+			_ => { None }
+		};
+
+		if b.is_some() {
+			let mut u = Unit::new();
+			u.insert(b.unwrap(), 1f64);
+
+			let mut q = Quantity::new_rational(1f64).unwrap();
+			q.set_unit(u);
+
+			return Some(q);
+		};
+
+		// Compound units
+		let b = match s {
+			"ft" => Some(CompoundUnit::FOOT),
+			_ => { None }
+		};
+
+		if b.is_some() {
+			let b = b.unwrap();
+			let q = Quantity{
+				v: b.coef(),
+				u: b.unit()
+			};
+			return Some(q);
+		};
+
+		return None;
+	}
+
 }
 
 
diff --git a/src/quantity/unit.rs b/src/quantity/unit.rs
index f45c7bd..493b68f 100644
--- a/src/quantity/unit.rs
+++ b/src/quantity/unit.rs
@@ -1,11 +1,11 @@
-use std::{collections::HashMap, hash::Hash};
-
-
+use std::collections::HashMap;
 use std::ops::{
 	Mul, Div,
 	MulAssign, DivAssign
 };
 
+use crate::quantity::Scalar;
+
 #[derive(Debug)]
 #[derive(Hash)]
 #[derive(Eq, PartialEq)]
@@ -20,6 +20,40 @@ pub enum BaseUnit {
 	Candela
 }
 
+pub struct CompoundUnit {
+	coef_str: &'static str,
+	rational: bool,
+	units: &'static[(BaseUnit, f64)],
+	pub str: &'static str
+}
+
+impl CompoundUnit {
+	pub const FOOT: CompoundUnit = CompoundUnit {
+		coef_str: "0.3048",
+		rational: false,
+		units: &[(BaseUnit::Meter, 1f64)],
+		str: "ft"
+	};
+
+	pub fn unit(&self) -> Unit {
+		let mut n = Unit::new();
+		for (u, p) in self.units.iter() {
+			n.insert(*u, *p);
+		}
+		return n;
+	}
+
+	pub fn coef(&self) -> Scalar {
+		if self.rational {
+			Scalar::new_rational_from_string(self.coef_str).unwrap()
+		} else {
+			Scalar::new_float_from_string(self.coef_str).unwrap()
+		}
+	}
+}
+
+
+
 #[derive(Debug)]
 #[derive(Clone)]
 pub struct Unit {
@@ -117,23 +151,6 @@ impl Unit {
 		};
 		return u;
 	}
-
-	pub fn from_string(s: &str) -> Option<Unit> {
-		let b = match s {
-			"m" => BaseUnit::Meter,
-			"s" => BaseUnit::Second,
-			"kg" => BaseUnit::Kilogram,
-			"a" => BaseUnit::Ampere,
-			"k" => BaseUnit::Kelvin,
-			"mol" => BaseUnit::Mole,
-			"c" => BaseUnit::Candela,
-			_ => { return None; }
-		};
-
-		let mut u = Unit::new();
-		u.insert(b, 1f64);
-		return Some(u);
-	}
 }