diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,8 @@
 # Change Log
 
+## [0.4.1.0] - 2016-11-24
+- Add `withSized` and `withSizedList`
+
 ## [0.4.0.1] - 2016-11-12
 - Raise lower bound on base to 4.9
 
diff --git a/src/Data/Vector/Generic/Sized.hs b/src/Data/Vector/Generic/Sized.hs
--- a/src/Data/Vector/Generic/Sized.hs
+++ b/src/Data/Vector/Generic/Sized.hs
@@ -8,6 +8,7 @@
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE RankNTypes #-}
 
 {-|
 This module reexports the functionality in 'Data.Vector.Generic' which maps well
@@ -212,10 +213,12 @@
   , fromList
   , fromListN
   , fromListN'
+  , withSizedList
     -- ** Other Vector types
   , convert
     -- ** Unsized Vectors
   , toSized
+  , withSized
   , fromSized
   , withVectorUnsafe
   ) where
@@ -1525,6 +1528,17 @@
 fromListN' _ = fromListN
 {-# inline fromListN' #-}
 
+-- | /O(n)/ Takes a list and returns a continuation providing a vector with
+-- a size parameter corresponding to the length of the list.
+--
+-- Essentially converts a list into a vector with the proper size
+-- parameter, determined at runtime.
+--
+-- See 'withSized'
+withSizedList :: forall v a r. VG.Vector v a
+              => [a] -> (forall n. KnownNat n => Vector v n a -> r) -> r
+withSizedList xs = withSized (VG.fromList xs)
+
 -- ** Different Vector types
 
 -- | /O(n)/ Convert different vector types
@@ -1545,6 +1559,19 @@
   where n' = natVal (Proxy :: Proxy n)
 {-# inline toSized #-}
 
+-- | Takes a 'Data.Vector.Generic.Vector' and returns a continuation
+-- providing a 'Data.Vector.Generic.Sized' with a size parameter @n@ that
+-- is determined at runtime based on the length of the input vector.
+--
+-- Essentially converts a 'Data.Vector.Generic.Vector' into
+-- a 'Data.Vector.Generic.Sized.Vector' with the correct size parameter
+-- @n@.
+withSized :: forall v a r. VG.Vector v a
+          => v a -> (forall n. KnownNat n => Vector v n a -> r) -> r
+withSized v f = case someNatVal (fromIntegral (VG.length v)) of
+    Just (SomeNat (Proxy :: Proxy n)) -> f (Vector v :: Vector v n a)
+    Nothing -> error "withSized: VG.length returned negative length."
+
 fromSized :: Vector v n a -> v a
 fromSized (Vector v) = v
 {-# inline fromSized #-}
@@ -1555,4 +1582,3 @@
                  => (v a -> w b) -> Vector v n a -> Vector w n b
 withVectorUnsafe f (Vector v) = Vector (f v)
 {-# inline withVectorUnsafe #-}
-
diff --git a/src/Data/Vector/Sized.hs b/src/Data/Vector/Sized.hs
--- a/src/Data/Vector/Sized.hs
+++ b/src/Data/Vector/Sized.hs
@@ -5,6 +5,7 @@
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE RankNTypes #-}
 
 {-|
 This module re-exports the functionality in 'Data.Vector.Generic.Sized'
@@ -209,8 +210,10 @@
   , fromList
   , fromListN
   , fromListN'
+  , withSizedList
     -- ** Unsized Vectors
   , toSized
+  , withSized
   , fromSized
   , withVectorUnsafe
   ) where
@@ -1392,6 +1395,17 @@
 fromListN' = V.fromListN'
 {-# inline fromListN' #-}
 
+-- | /O(n)/ Takes a list and returns a continuation providing a vector with
+-- a size parameter corresponding to the length of the list.
+--
+-- Essentially converts a list into a vector with the proper size
+-- parameter, determined at runtime.
+--
+-- See 'withSized'
+withSizedList :: forall a r. [a] -> (forall n. KnownNat n => Vector n a -> r) -> r
+withSizedList xs = withSized (VU.fromList xs)
+{-# inline withSizedList #-}
+
 -- ** Unsized vectors
 
 -- | Convert a 'Data.Vector.Generic.Vector' into a
@@ -1401,6 +1415,17 @@
         => VU.Vector a -> Maybe (Vector n a)
 toSized = V.toSized
 {-# inline toSized #-}
+
+-- | Takes a 'Data.Vector.Vector' and returns a continuation providing
+-- a 'Data.Vector.Sized.Vector' with a size parameter @n@ that is
+-- determined at runtime based on the length of the input vector.
+--
+-- Essentially converts a 'Data.Vector.Vector' into
+-- a 'Data.Vector.Sized.Vector' with the correct size parameter
+-- @n@.
+withSized :: forall a r. VU.Vector a -> (forall n. KnownNat n => Vector n a -> r) -> r
+withSized = V.withSized
+{-# inline withSized #-}
 
 fromSized :: Vector n a -> VU.Vector a
 fromSized = V.fromSized
diff --git a/src/Data/Vector/Storable/Sized.hs b/src/Data/Vector/Storable/Sized.hs
--- a/src/Data/Vector/Storable/Sized.hs
+++ b/src/Data/Vector/Storable/Sized.hs
@@ -5,6 +5,7 @@
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE RankNTypes #-}
 
 {-|
 This module re-exports the functionality in 'Data.Vector.Generic.Sized'
@@ -209,8 +210,10 @@
   , fromList
   , fromListN
   , fromListN'
+  , withSizedList
     -- ** Unsized Vectors
   , toSized
+  , withSized
   , fromSized
   , withVectorUnsafe
   ) where
@@ -1447,6 +1450,18 @@
 fromListN' = V.fromListN'
 {-# inline fromListN' #-}
 
+-- | /O(n)/ Takes a list and returns a continuation providing a vector with
+-- a size parameter corresponding to the length of the list.
+--
+-- Essentially converts a list into a vector with the proper size
+-- parameter, determined at runtime.
+--
+-- See 'withSized'
+withSizedList :: forall a r. Storable a
+              => [a] -> (forall n. KnownNat n => Vector n a -> r) -> r
+withSizedList xs = withSized (VS.fromList xs)
+{-# inline withSizedList #-}
+
 -- ** Unsized vectors
 
 -- | Convert a 'Data.Vector.Generic.Vector' into a
@@ -1456,6 +1471,19 @@
         => VS.Vector a -> Maybe (Vector n a)
 toSized = V.toSized
 {-# inline toSized #-}
+
+-- | Takes a 'Data.Vector.Storable.Vector' and returns a continuation
+-- providing a 'Data.Vector.Storable.Sized.Vector' with a size parameter
+-- @n@ that is determined at runtime based on the length of the input
+-- vector.
+--
+-- Essentially converts a 'Data.Vector.Storable.Vector' into
+-- a 'Data.Vector.Storable.Sized.Vector' with the correct size parameter
+-- @n@.
+withSized :: forall a r. Storable a
+          => VS.Vector a -> (forall n. KnownNat n => Vector n a -> r) -> r
+withSized = V.withSized
+{-# inline withSized #-}
 
 fromSized :: Vector n a -> VS.Vector a
 fromSized = V.fromSized
diff --git a/vector-sized.cabal b/vector-sized.cabal
--- a/vector-sized.cabal
+++ b/vector-sized.cabal
@@ -1,5 +1,5 @@
 name:                vector-sized
-version:             0.4.0.1
+version:             0.4.1.0
 synopsis:            Size tagged vectors
 description:         Please see README.md
 homepage:            http://github.com/expipiplus1/vector-sized#readme