diff --git a/src/NzbDrone.Common.Test/ExtensionTests/Int64ExtensionFixture.cs b/src/NzbDrone.Common.Test/ExtensionTests/Int64ExtensionFixture.cs
new file mode 100644
index 000000000..5984e45ec
--- /dev/null
+++ b/src/NzbDrone.Common.Test/ExtensionTests/Int64ExtensionFixture.cs
@@ -0,0 +1,19 @@
+using FluentAssertions;
+using NUnit.Framework;
+using NzbDrone.Common.Extensions;
+
+namespace NzbDrone.Common.Test.ExtensionTests
+{
+    [TestFixture]
+    public class Int64ExtensionFixture
+    {
+        [TestCase(1000, "1.0 KB")]
+        [TestCase(1000000, "1.0 MB")]
+        [TestCase(377487360, "377.5 MB")]
+        [TestCase(1255864686, "1.3 GB")]
+        public void should_calculate_string_correctly(long bytes, string expected)
+        {
+            bytes.SizeSuffix().Should().Be(expected);
+        }
+    }
+}
diff --git a/src/NzbDrone.Common.Test/NzbDrone.Common.Test.csproj b/src/NzbDrone.Common.Test/NzbDrone.Common.Test.csproj
index a4199d64b..f0c402849 100644
--- a/src/NzbDrone.Common.Test/NzbDrone.Common.Test.csproj
+++ b/src/NzbDrone.Common.Test/NzbDrone.Common.Test.csproj
@@ -75,6 +75,7 @@
     <Compile Include="EnvironmentProviderTest.cs" />
     <Compile Include="EnvironmentTests\EnvironmentProviderTest.cs" />
     <Compile Include="EnvironmentTests\StartupArgumentsFixture.cs" />
+    <Compile Include="ExtensionTests\Int64ExtensionFixture.cs" />
     <Compile Include="Http\HttpClientFixture.cs" />
     <Compile Include="Http\HttpRequestBuilderFixture.cs" />
     <Compile Include="Http\HttpRequestFixture.cs" />
diff --git a/src/NzbDrone.Common/Extensions/Int64Extensions.cs b/src/NzbDrone.Common/Extensions/Int64Extensions.cs
index d389e5969..9021cfde3 100644
--- a/src/NzbDrone.Common/Extensions/Int64Extensions.cs
+++ b/src/NzbDrone.Common/Extensions/Int64Extensions.cs
@@ -8,11 +8,13 @@ namespace NzbDrone.Common.Extensions
 
         public static string SizeSuffix(this Int64 value)
         {
-            if (value < 0) { return "-" + SizeSuffix(-value); }
-            if (value == 0) { return "0.0 bytes"; }
+            const int bytesInKb = 1000;
 
-            var mag = (int)Math.Log(value, 1024);
-            decimal adjustedSize = (decimal)value / (1L << (mag * 10));
+            if (value < 0) return "-" + SizeSuffix(-value);
+            if (value == 0) return "0 bytes";
+            
+            var mag = (int)Math.Log(value, bytesInKb);
+            var adjustedSize = value / (decimal)Math.Pow(bytesInKb, mag);
 
             return string.Format("{0:n1} {1}", adjustedSize, SizeSuffixes[mag]);
         }