diff --git a/include/Pomdog/Math/MathHelper.hpp b/include/Pomdog/Math/MathHelper.hpp
index 2a6edfeb3..10925f003 100644
--- a/include/Pomdog/Math/MathHelper.hpp
+++ b/include/Pomdog/Math/MathHelper.hpp
@@ -4,8 +4,6 @@
 
 #include "Pomdog/Math/Degree.hpp"
 #include "Pomdog/Math/Radian.hpp"
-#include <cstdint>
-#include <cfloat>
 #include <type_traits>
 
 namespace Pomdog {
@@ -95,7 +93,7 @@ T SmoothStep(T const& min, T const& max, T const& amount)
 }
 //-------------------------------------------------------------------
 template <typename T>
-Radian<T> ToRadians(Degree<T> const& degrees) noexcept
+Radian<T> ToRadians(const Degree<T>& degrees) noexcept
 {
     static_assert(std::is_floating_point<T>::value, "");
     constexpr auto scaleFactor = MathConstants<T>::Pi() * (T{1} / T{180});
@@ -103,12 +101,28 @@ Radian<T> ToRadians(Degree<T> const& degrees) noexcept
 }
 //-------------------------------------------------------------------
 template <typename T>
-Degree<T> ToDegrees(Radian<T> const& radians) noexcept
+Radian<T> ToRadians(const T& degrees) noexcept
+{
+    static_assert(std::is_floating_point<T>::value, "");
+    constexpr auto scaleFactor = MathConstants<T>::Pi() * (T{1} / T{180});
+    return Radian<T>(degrees * scaleFactor);
+}
+//-------------------------------------------------------------------
+template <typename T>
+Degree<T> ToDegrees(const Radian<T>& radians) noexcept
 {
     static_assert(std::is_floating_point<T>::value, "");
     constexpr auto scaleFactor = T{180} * (T{1} / MathConstants<T>::Pi());
     return Degree<T>(radians.value * scaleFactor);
 }
+//-------------------------------------------------------------------
+template <typename T>
+Degree<T> ToDegrees(const T& radians) noexcept
+{
+    static_assert(std::is_floating_point<T>::value, "");
+    constexpr auto scaleFactor = T{180} * (T{1} / MathConstants<T>::Pi());
+    return Degree<T>(radians * scaleFactor);
+}
 
 } // namespace MathHelper
 } // namespace Pomdog
diff --git a/test/FrameworkTest/Math/MathHelperTest.cpp b/test/FrameworkTest/Math/MathHelperTest.cpp
index da4bbecf2..b3f139985 100644
--- a/test/FrameworkTest/Math/MathHelperTest.cpp
+++ b/test/FrameworkTest/Math/MathHelperTest.cpp
@@ -4,6 +4,8 @@
 #include <gtest/iutest_switch.hpp>
 
 namespace MathHelper = Pomdog::MathHelper;
+using Pomdog::Degree;
+using Pomdog::Radian;
 
 TEST(MathHelper, Clamp)
 {
@@ -110,3 +112,35 @@ TEST(MathHelper, SmoothStep)
     EXPECT_LT(MathHelper::SmoothStep(0.0f, 1.0f, 0.8f), MathHelper::SmoothStep(0.0f, 1.0f, 0.9f));
     EXPECT_LT(MathHelper::SmoothStep(0.0f, 1.0f, 0.9f), MathHelper::SmoothStep(0.0f, 1.0f, 1.0f));
 }
+
+TEST(MathHelper, ToDegrees)
+{
+    constexpr auto epsilon = 0.0000001f;
+    EXPECT_NEAR(0.0f, MathHelper::ToDegrees(0.0f).value, epsilon);
+    EXPECT_NEAR(45.0f, MathHelper::ToDegrees(0.7853981633f).value, epsilon);
+    EXPECT_NEAR(90.0f, MathHelper::ToDegrees(1.5707963267f).value, epsilon);
+    EXPECT_NEAR(180.0f, MathHelper::ToDegrees(3.1415926535f).value, epsilon);
+    EXPECT_NEAR(360.0f, MathHelper::ToDegrees(6.2831853071f).value, epsilon);
+
+    EXPECT_NEAR(0.0f, MathHelper::ToDegrees(Radian<float>(0.0f)).value, epsilon);
+    EXPECT_NEAR(45.0f, MathHelper::ToDegrees(Radian<float>(0.7853981633f)).value, epsilon);
+    EXPECT_NEAR(90.0f, MathHelper::ToDegrees(Radian<float>(1.5707963267f)).value, epsilon);
+    EXPECT_NEAR(180.0f, MathHelper::ToDegrees(Radian<float>(3.1415926535f)).value, epsilon);
+    EXPECT_NEAR(360.0f, MathHelper::ToDegrees(Radian<float>(6.2831853071f)).value, epsilon);
+}
+
+TEST(MathHelper, ToRadians)
+{
+    constexpr auto epsilon = 0.0000005f;
+    EXPECT_NEAR(0.0f, MathHelper::ToRadians(0.0f).value, epsilon);
+    EXPECT_NEAR(0.7853981633f, MathHelper::ToRadians(45.0f).value, epsilon);
+    EXPECT_NEAR(1.5707963267f, MathHelper::ToRadians(90.0f).value, epsilon);
+    EXPECT_NEAR(3.1415926535f, MathHelper::ToRadians(180.0f).value, epsilon);
+    EXPECT_NEAR(6.2831853071f, MathHelper::ToRadians(360.0f).value, epsilon);
+
+    EXPECT_NEAR(0.0f, MathHelper::ToRadians(Degree<float>(0.0f)).value, epsilon);
+    EXPECT_NEAR(0.7853981633f, MathHelper::ToRadians(Degree<float>(45.0f)).value, epsilon);
+    EXPECT_NEAR(1.5707963267f, MathHelper::ToRadians(Degree<float>(90.0f)).value, epsilon);
+    EXPECT_NEAR(3.1415926535f, MathHelper::ToRadians(Degree<float>(180.0f)).value, epsilon);
+    EXPECT_NEAR(6.2831853071f, MathHelper::ToRadians(Degree<float>(360.0f)).value, epsilon);
+}