diff --git a/src/gui/kernel/qhighdpiscaling.cpp b/src/gui/kernel/qhighdpiscaling.cpp
index 7107e37e40..726b7bc4b2 100644
--- a/src/gui/kernel/qhighdpiscaling.cpp
+++ b/src/gui/kernel/qhighdpiscaling.cpp
@@ -294,7 +294,9 @@ qreal QHighDpiScaling::rawScaleFactor(const QPlatformScreen *screen)
     qreal factor;
     QDpi platformBaseDpi = screen->logicalBaseDpi();
     if (usePhysicalDpi) {
-        qreal platformPhysicalDpi = screen->screen()->physicalDotsPerInch();
+        QSize sz = screen->geometry().size();
+        QSizeF psz = screen->physicalSize();
+        qreal platformPhysicalDpi = ((sz.height() / psz.height()) + (sz.width() / psz.width())) * qreal(25.4 * 0.5);
         factor = qreal(platformPhysicalDpi) / qreal(platformBaseDpi.first);
     } else {
         const QDpi platformLogicalDpi = QPlatformScreen::overrideDpi(screen->logicalDpi());