diff --git a/grenade.cabal b/grenade.cabal
index f8e90dc..97e0164 100644
--- a/grenade.cabal
+++ b/grenade.cabal
@@ -43,6 +43,7 @@ library
                      , containers                      >= 0.5         && < 0.6
                      , cereal                          >= 0.5         && < 0.6
                      , deepseq                         >= 1.4         && < 1.5
+                     , exceptions
                      , hmatrix                         == 0.18.*
                      , MonadRandom                     >= 0.4         && < 0.6
                      , primitive                       >= 0.6         && < 0.7
@@ -106,6 +107,8 @@ library
                        Grenade.Recurrent.Layers.LSTM
 
                        Grenade.Utils.OneHot
+                       Grenade.Utils.Accuracy
+                       Grenade.Utils.Accuracy.Internal
 
   includes:            cbits/im2col.h
                        cbits/gradient_descent.h
diff --git a/src/Grenade/Utils/Accuracy.hs b/src/Grenade/Utils/Accuracy.hs
new file mode 100644
index 0000000..9fa2f69
--- /dev/null
+++ b/src/Grenade/Utils/Accuracy.hs
@@ -0,0 +1,30 @@
+{-# LANGUAGE DeriveGeneric #-}
+
+module Grenade.Utils.Accuracy
+    ( Accuracy
+    , HyperParamAccuracy(..)
+    , accuracyM
+    ) where
+
+import Grenade.Core.LearningParameters
+
+import Grenade.Utils.Accuracy.Internal
+
+import GHC.Generics
+
+import Data.Validity
+
+import Data.Aeson (ToJSON, FromJSON)
+
+data HyperParamAccuracy = HyperParamAccuracy
+    { hyperParam :: LearningParameters
+    , testAccuracies :: [Accuracy]
+    , validationAccuracies :: [Accuracy]
+    , trainAccuracies :: [Accuracy]
+    } deriving (Show, Eq, Generic)
+
+instance ToJSON HyperParamAccuracy
+
+instance FromJSON HyperParamAccuracy
+
+instance Validity HyperParamAccuracy
diff --git a/src/Grenade/Utils/Accuracy/Internal.hs b/src/Grenade/Utils/Accuracy/Internal.hs
new file mode 100644
index 0000000..e9ceb76
--- /dev/null
+++ b/src/Grenade/Utils/Accuracy/Internal.hs
@@ -0,0 +1,30 @@
+{-# LANGUAGE DeriveGeneric #-}
+
+module Grenade.Utils.Accuracy.Internal where
+
+import Data.Validity
+
+import Control.Monad.Catch
+
+import Data.Aeson (ToJSON, FromJSON)
+
+import GHC.Generics
+
+newtype Accuracy = Accuracy Double deriving (Show, Eq, Generic)
+
+data AccuracyNotInRange = AccuracyNotInRange deriving (Show, Eq)
+
+instance Exception AccuracyNotInRange where
+    displayException AccuracyNotInRange = "The accuracy is not in [0,1]."
+
+accuracyM :: MonadThrow m => Double -> m Accuracy
+accuracyM x = case 0 <= x && x <= 1 of
+    False -> throwM AccuracyNotInRange
+    True -> pure $ Accuracy x
+
+instance ToJSON Accuracy
+
+instance FromJSON Accuracy
+
+instance Validity Accuracy where
+    validate (Accuracy x) = 0 <= x && x <= 1 <?@> "The accuracy is in [0,1]"
diff --git a/test/Test/Grenade/Gen.hs b/test/Test/Grenade/Gen.hs
index a99c1b5..7542e77 100644
--- a/test/Test/Grenade/Gen.hs
+++ b/test/Test/Grenade/Gen.hs
@@ -6,6 +6,10 @@ import Grenade.Core.LearningParameters
 
 import Data.GenValidity
 
+import Grenade.Utils.Accuracy
+import Grenade.Utils.Accuracy.Internal
+
+import Test.QuickCheck (choose, listOf)
 import Test.QuickCheck.Gen (suchThat)
 
 instance GenUnchecked LearningParameters
@@ -15,3 +19,17 @@ instance GenValid LearningParameters where
         rate <- genValid `suchThat` (> 0)
         momentum <- genValid `suchThat` (>= 0)
         LearningParameters rate momentum <$> genValid `suchThat` (>= 0)
+
+instance GenUnchecked Accuracy
+
+instance GenValid Accuracy where
+    genValid = Accuracy <$> choose (0,1)
+
+instance GenUnchecked HyperParamAccuracy
+
+instance GenValid HyperParamAccuracy where
+    genValid = do
+        param <- genValid
+        testAcc <- listOf genValid
+        validationAcc <- listOf genValid
+        HyperParamAccuracy param testAcc validationAcc <$> listOf genValid
diff --git a/test/Test/Grenade/InstanceSpec.hs b/test/Test/Grenade/InstanceSpec.hs
index 9e27b51..73a1d8e 100644
--- a/test/Test/Grenade/InstanceSpec.hs
+++ b/test/Test/Grenade/InstanceSpec.hs
@@ -8,6 +8,7 @@ import Test.Hspec
 import Test.Grenade.Gen ()
 
 import Grenade.Core.LearningParameters
+import Grenade.Utils.Accuracy
 
 import Test.Validity
 import Test.Validity.Aeson
@@ -19,3 +20,7 @@ spec :: Spec
 spec = do
     genValidSpec @LearningParameters
     jsonSpecOnValid @LearningParameters
+    genValidSpec @Accuracy
+    jsonSpecOnValid @Accuracy
+    genValidSpec @HyperParamAccuracy
+    jsonSpecOnValid @HyperParamAccuracy