diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,9 @@
+Version 1.0.1
+-------------
+
+ * Added derived SI units.
+ * Added British-spelled synonyms for SI units.
+
 Version 1.0
 -----------
 
diff --git a/Data/Metrology/SI/Units.hs b/Data/Metrology/SI/Units.hs
--- a/Data/Metrology/SI/Units.hs
+++ b/Data/Metrology/SI/Units.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE TypeFamilies, TypeOperators #-}
+{-# LANGUAGE TypeFamilies, TypeOperators, PatternSynonyms #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -12,15 +12,24 @@
 -- This module exports unit definitions according to the SI system of units.
 -- The definitions were taken from here: <http://www.bipm.org/en/si/>.
 --
+-- Some additional units were added base on
+-- <http://www.bipm.org/en/si/si_brochure/chapter4/table6.html this link>:
+-- "Non-SI units accepted for use with the SI,
+-- and units based on fundamental constants".
+--
 -- There is one deviation from the definition at that site: To work better
 -- with prefixes, the unit of mass is 'Gram'.
+--
+-- This module exports both American spellings and British spellings of
+-- units, using pattern synonyms to get the British spellings of data
+-- constructors.
 -----------------------------------------------------------------------------
 
 module Data.Metrology.SI.Units where
 
 import Data.Metrology
 import Data.Metrology.SI.Dims
-import Data.Metrology.SI.Prefixes ( Centi )
+import Data.Metrology.SI.Prefixes ( Kilo, Centi )
 
 data Meter = Meter
 instance Unit Meter where
@@ -29,6 +38,9 @@
 instance Show Meter where
   show _ = "m"
 
+type Metre = Meter
+pattern Metre = Meter
+
 data Gram = Gram
 instance Unit Gram where
   type BaseUnit Gram = Canonical
@@ -43,6 +55,29 @@
 instance Show Second where
   show _ = "s"
 
+-- | Derived SI unit
+data Minute = Minute
+instance Unit Minute where
+  type BaseUnit Minute = Second
+  conversionRatio _ = 60
+instance Show Minute where
+  show _ = "min"
+
+-- | Derived SI unit
+data Hour = Hour
+instance Unit Hour where
+  type BaseUnit Hour = Minute
+  conversionRatio _ = 60
+instance Show Hour where
+  show _ = "h"
+
+data Day = Day
+instance Unit Day where
+  type BaseUnit Day = Hour
+  conversionRatio _ = 24
+instance Show Day where
+  show _ = "d"
+
 data Ampere = Ampere
 instance Unit Ampere where
   type BaseUnit Ampere = Canonical
@@ -85,6 +120,9 @@
 instance Show Liter where
   show _ = "l"
 
+type Litre = Liter
+pattern Litre = Liter
+
 data Newton = Newton
 instance Unit Newton where
   type BaseUnit Newton = Gram :* Meter :/ (Second :^ Two)
@@ -194,3 +232,21 @@
 instance Show Katal where
   show _ = "kat"
 
+-- | Derived SI unit
+data Hectare = Hectare
+instance Unit Hectare where
+  type BaseUnit Hectare = Meter :^ Two
+  conversionRatio _ = 10000
+instance Show Hectare where
+  show _ = "ha"
+
+-- | Derived SI unit
+data Ton = Ton
+instance Unit Ton where
+  type BaseUnit Ton = Kilo :@ Gram
+  conversionRatio _ = 1000
+instance Show Ton where
+  show _ = "t"
+
+type Tonne = Ton
+pattern Tonne = Ton
diff --git a/units-defs.cabal b/units-defs.cabal
--- a/units-defs.cabal
+++ b/units-defs.cabal
@@ -1,5 +1,5 @@
 name:           units-defs
-version:        1.0
+version:        1.0.1
 cabal-version:  >= 1.10
 synopsis:       Definitions for use with the units package
 homepage:       http://github.com/goldfirere/units-defs
@@ -23,7 +23,7 @@
 source-repository this
   type:     git
   location: https://github.com/goldfirere/units-defs.git
-  tag:      v1.0
+  tag:      v1.0.1
 
 library
   build-depends: