diff --git a/src/citra/emu_window/emu_window_glfw.cpp b/src/citra/emu_window/emu_window_glfw.cpp
index 02f524e03..7c43214cc 100644
--- a/src/citra/emu_window/emu_window_glfw.cpp
+++ b/src/citra/emu_window/emu_window_glfw.cpp
@@ -18,6 +18,10 @@ static void OnWindowSizeEvent(GLFWwindow* win, int width, int height) {
     emu_window->SetClientAreaHeight(height);
 }
 
+void EmuWindow_GLFW::GetFramebufferSize(int* fbWidth, int* fbHeight) {
+    glfwGetFramebufferSize(m_render_window, fbWidth, fbHeight);
+}
+
 /// EmuWindow_GLFW constructor
 EmuWindow_GLFW::EmuWindow_GLFW() {
     // Initialize the window
@@ -48,6 +52,7 @@ EmuWindow_GLFW::EmuWindow_GLFW() {
     //glfwSetKeyCallback(m_render_window, OnKeyEvent);
     //glfwSetWindowSizeCallback(m_render_window, OnWindowSizeEvent);
 
+
     DoneCurrent();
 }
 
diff --git a/src/citra/emu_window/emu_window_glfw.h b/src/citra/emu_window/emu_window_glfw.h
index c1b41203b..ee7c03251 100644
--- a/src/citra/emu_window/emu_window_glfw.h
+++ b/src/citra/emu_window/emu_window_glfw.h
@@ -17,7 +17,7 @@ public:
     void SwapBuffers();
 
 	/// Polls window events
-	void PollEvents();
+    void PollEvents();
 
     /// Makes the graphics context current for the caller thread
     void MakeCurrent();
@@ -25,6 +25,9 @@ public:
     /// Releases (dunno if this is the "right" word) the GLFW context from the caller thread
     void DoneCurrent();
 
+    /// Gets the size of the window in pixels
+    void GetFramebufferSize(int* fbWidth, int* fbHeight);
+
 	GLFWwindow* m_render_window;    ///< Internal GLFW render window
 
 private:
diff --git a/src/citra_qt/bootmanager.cpp b/src/citra_qt/bootmanager.cpp
index 573060d30..8a770925b 100644
--- a/src/citra_qt/bootmanager.cpp
+++ b/src/citra_qt/bootmanager.cpp
@@ -179,6 +179,24 @@ void GRenderWindow::PollEvents() {
     */
 }
 
+// On Qt 5.1+, this correctly gets the size of the framebuffer (pixels).
+//
+// Older versions get the window size (density independent pixels),
+// and hence, do not support DPI scaling ("retina" displays).
+// The result will be a viewport that is smaller than the extent of the window.
+void GRenderWindow::GetFramebufferSize(int* fbWidth, int* fbHeight)
+{
+#if QT_VERSION >= QT_VERSION_CHECK(5, 1, 0)
+    int pixelRatio = child->QPaintDevice::devicePixelRatio();
+    
+    *fbWidth = child->QPaintDevice::width() * pixelRatio;
+    *fbHeight = child->QPaintDevice::height() * pixelRatio;
+#else
+    *fbWidth = child->QPaintDevice::width();
+    *fbHeight = child->QPaintDevice::height();
+#endif
+}
+
 void GRenderWindow::BackupGeometry()
 {
     geometry = ((QGLWidget*)this)->saveGeometry();
diff --git a/src/citra_qt/bootmanager.hxx b/src/citra_qt/bootmanager.hxx
index 51cb781e9..0cd9b3ed5 100644
--- a/src/citra_qt/bootmanager.hxx
+++ b/src/citra_qt/bootmanager.hxx
@@ -96,6 +96,7 @@ public:
     void MakeCurrent();
     void DoneCurrent();
     void PollEvents();
+    void GetFramebufferSize(int* fbWidth, int* fbHeight);
 
     void BackupGeometry();
     void RestoreGeometry();
diff --git a/src/common/emu_window.h b/src/common/emu_window.h
index 5e2c33d7a..bb1f5aecf 100644
--- a/src/common/emu_window.h
+++ b/src/common/emu_window.h
@@ -32,6 +32,9 @@ public:
     /// Releases (dunno if this is the "right" word) the GLFW context from the caller thread
     virtual void DoneCurrent() = 0;
 
+    /// Gets the size of the window in pixels
+    virtual void GetFramebufferSize(int* fbWidth, int* fbHeight) = 0;
+
     Config GetConfig() const { 
         return m_config;
     }
diff --git a/src/video_core/renderer_opengl/renderer_opengl.cpp b/src/video_core/renderer_opengl/renderer_opengl.cpp
index 0e4e06517..4f0eb8213 100644
--- a/src/video_core/renderer_opengl/renderer_opengl.cpp
+++ b/src/video_core/renderer_opengl/renderer_opengl.cpp
@@ -191,7 +191,8 @@ void RendererOpenGL::InitFramebuffer() {
 }
 
 void RendererOpenGL::RenderFramebuffer() {
-    glViewport(0, 0, resolution_width, resolution_height);
+    UpdateViewportExtent();
+    glViewport(viewport_extent.x, viewport_extent.y, viewport_extent.width, viewport_extent.height);
     glClear(GL_COLOR_BUFFER_BIT);
 
     glUseProgram(program_id);
@@ -243,6 +244,43 @@ void RendererOpenGL::SetWindow(EmuWindow* window) {
     render_window = window;
 }
 
+// TODO: This should happen on window resize callback from EmuWindow.
+//       It should be done when EmuWindow is refactored.
+void RendererOpenGL::UpdateViewportExtent() {
+    int width_in_pixels;
+    int height_in_pixels;
+
+    render_window->GetFramebufferSize(&width_in_pixels, &height_in_pixels);
+
+    // No update needed if framebuffer size hasn't changed
+    if (width_in_pixels == framebuffer_size.width && height_in_pixels == framebuffer_size.height) {
+        return;
+    }
+
+    // Letterbox the emulation content into the window
+    framebuffer_size.width = width_in_pixels;
+    framebuffer_size.height = height_in_pixels;
+
+    float windowRatio = static_cast<float>(height_in_pixels) / width_in_pixels;
+    float emulationRatio = static_cast<float>(resolution_height) / resolution_width;
+
+    // If the window is more narrow than the emulation content, borders are applied on the
+    // top and bottom of the window
+    if (windowRatio > emulationRatio) {
+        viewport_extent.width = width_in_pixels;
+        viewport_extent.height = emulationRatio * viewport_extent.width;
+        viewport_extent.x = 0;
+        viewport_extent.y = (height_in_pixels - viewport_extent.height) / 2;
+
+    // Otherwise, borders are applied on the left and right sides of the window
+    } else {
+        viewport_extent.height  = height_in_pixels;
+        viewport_extent.width   = (1 / emulationRatio) * viewport_extent.height;
+        viewport_extent.x = (width_in_pixels - viewport_extent.width) / 2;
+        viewport_extent.y = 0;
+    }
+}
+
 /// Initialize the renderer
 void RendererOpenGL::Init() {
     render_window->MakeCurrent();
diff --git a/src/video_core/renderer_opengl/renderer_opengl.h b/src/video_core/renderer_opengl/renderer_opengl.h
index eac91df51..fe7375fca 100644
--- a/src/video_core/renderer_opengl/renderer_opengl.h
+++ b/src/video_core/renderer_opengl/renderer_opengl.h
@@ -52,6 +52,9 @@ private:
     /// Updates the framerate
     void UpdateFramerate();
 
+    /// Updates the viewport rectangle
+    void UpdateViewportExtent();
+
     /// Structure used for storing information for rendering each 3DS screen
     struct ScreenInfo {
         // Properties
@@ -81,6 +84,18 @@ private:
     int resolution_width;                         ///< Current resolution width
     int resolution_height;                        ///< Current resolution height
 
+    struct {
+        int width;
+        int height;
+    } framebuffer_size;                           ///< Current framebuffer size
+
+    struct {
+        int x;
+        int y;
+        int width;
+        int height;
+    } viewport_extent;                            ///< Current viewport rectangle
+
     // OpenGL global object IDs
     GLuint vertex_array_id;
     GLuint program_id;