diff --git a/gdk/gdkmonitor.c b/gdk/gdkmonitor.c
index 685a5ad62f..b33c60ed88 100644
--- a/gdk/gdkmonitor.c
+++ b/gdk/gdkmonitor.c
@@ -744,3 +744,11 @@ gdk_monitor_set_description (GdkMonitor *monitor,
   g_object_notify_by_pspec (G_OBJECT (monitor), props[PROP_DESCRIPTION]);
 }
 
+#define MM_PER_INCH 25.4
+
+double
+gdk_monitor_get_dpi (GdkMonitor *monitor)
+{
+  return MAX ((monitor->geometry.width * monitor->scale) / (monitor->width_mm / MM_PER_INCH),
+              (monitor->geometry.height * monitor->scale) / (monitor->height_mm / MM_PER_INCH));
+}
diff --git a/gdk/gdkmonitorprivate.h b/gdk/gdkmonitorprivate.h
index a696fbce3c..88b5d818d0 100644
--- a/gdk/gdkmonitorprivate.h
+++ b/gdk/gdkmonitorprivate.h
@@ -76,6 +76,7 @@ void            gdk_monitor_set_subpixel_layout (GdkMonitor        *monitor,
 void            gdk_monitor_invalidate          (GdkMonitor *monitor);
 void            gdk_monitor_set_description     (GdkMonitor *monitor,
                                                  const char *description);
+double          gdk_monitor_get_dpi             (GdkMonitor *monitor);
 
 G_END_DECLS