diff --git a/src/Data/Quantity/Math.purs b/src/Data/Quantity/Math.purs
index 853c1aa..af3d144 100644
--- a/src/Data/Quantity/Math.purs
+++ b/src/Data/Quantity/Math.purs
@@ -33,6 +33,7 @@ module Data.Quantity.Math
   , pi
   , e
   , tau
+  , phi
   ) where
 
 import Prelude
@@ -149,3 +150,6 @@ e = scalar' Decimal.e
 
 tau ∷ Quantity
 tau = scalar' $ Decimal.fromNumber 2.0 * Decimal.pi
+
+phi ∷ Quantity
+phi = scalar' $ (one + Decimal.sqrt (Decimal.fromNumber 5.0)) / Decimal.fromNumber 2.0
diff --git a/src/Quantities.purs b/src/Quantities.purs
index 32c4366..d99fb6b 100644
--- a/src/Quantities.purs
+++ b/src/Quantities.purs
@@ -26,7 +26,7 @@ import Data.Quantity (ConversionError(..), Quantity, abs, approximatelyEqual, as
                       sqrt, toScalar, toScalar', toStandard, (.*), (⊕), (⊖), (⊗), (⊘)) as DQ
 import Data.Quantity.Math (acos, acosh, asin, asinh, atan, atan2, atanh, ceil, cos, cosh, e,
                            exp, factorial, floor, gamma, ln, log10, max, max2, mean, min,
-                           min2, modulo, pi, round, sin, sinh, tan, tanh, tau) as DQM
+                           min2, modulo, pi, round, sin, sinh, tan, tanh, tau, phi) as DQM
 import Data.Quantity.Physics (avogadroConstant, electronCharge, electronMass, g0,
                               gravitationalConstant, kB, planckConstant, protonMass,
                               idealGasConstant, speedOfLight, µ0, µB, α, ε0, ℏ) as DQP