diff --git a/lib/thumbnailview/previewitemdelegate.cpp b/lib/thumbnailview/previewitemdelegate.cpp
--- a/lib/thumbnailview/previewitemdelegate.cpp
+++ b/lib/thumbnailview/previewitemdelegate.cpp
@@ -164,7 +164,8 @@
         const int posX = mContextBarActions == PreviewItemDelegate::SelectionAction
             ? 0
             : (rect.width() - mContextBar->width()) / 2;
-        const int posY = qMax(CONTEXTBAR_MARGIN, mThumbnailSize.height() - thumbnailPix.height() - mContextBar->height());
+        const int thumbnailPixHeight = qRound(thumbnailPix.height() / thumbnailPix.devicePixelRatio());
+        const int posY = qMax(CONTEXTBAR_MARGIN, mThumbnailSize.height() - thumbnailPixHeight - mContextBar->height());
         mContextBar->move(rect.topLeft() + QPoint(posX, posY));
         mContextBar->show();
     }
@@ -317,13 +318,15 @@
     {
         const QPoint shadowOffset(-SHADOW_SIZE, -SHADOW_SIZE + 1);
 
-        int key = rect.height() * 1000 + rect.width();
+        const auto dpr = painter->device()->devicePixelRatioF();
+        int key = qRound((rect.height() * 1000 + rect.width()) * dpr);
 
         ShadowCache::Iterator it = mShadowCache.find(key);
         if (it == mShadowCache.end()) {
             QSize size = QSize(rect.width() + 2 * SHADOW_SIZE, rect.height() + 2 * SHADOW_SIZE);
             QColor color(0, 0, 0, SHADOW_STRENGTH);
-            QPixmap shadow = PaintUtils::generateFuzzyRect(size, color, SHADOW_SIZE);
+            QPixmap shadow = PaintUtils::generateFuzzyRect(size * dpr, color, qRound(SHADOW_SIZE * dpr));
+            shadow.setDevicePixelRatio(dpr);
             it = mShadowCache.insert(key, shadow);
         }
         painter->drawPixmap(rect.topLeft() + shadowOffset, it.value());
@@ -688,6 +691,7 @@
     int thumbnailHeight = d->mThumbnailSize.height();
     QSize fullSize;
     QPixmap thumbnailPix = d->mView->thumbnailForIndex(index, &fullSize);
+    QSize thumbnailSize = thumbnailPix.size() / thumbnailPix.devicePixelRatio();
     const KFileItem fileItem = fileItemForIndex(index);
     const bool opaque = !thumbnailPix.hasAlphaChannel();
     const bool isDirOrArchive = ArchiveUtils::fileItemIsDirOrArchive(fileItem);
@@ -739,10 +743,10 @@
 
     // Compute thumbnailRect
     QRect thumbnailRect = QRect(
-                              rect.left() + (rect.width() - thumbnailPix.width()) / 2,
-                              rect.top() + (thumbnailHeight - thumbnailPix.height()) + ITEM_MARGIN,
-                              thumbnailPix.width(),
-                              thumbnailPix.height());
+                              rect.left() + (rect.width() - thumbnailSize.width()) / 2,
+                              rect.top() + (thumbnailHeight - thumbnailSize.height()) + ITEM_MARGIN,
+                              thumbnailSize.width(),
+                              thumbnailSize.height());
 
     // Draw background
     const QRect backgroundRect = thumbnailRect.adjusted(-ITEM_MARGIN, -ITEM_MARGIN, ITEM_MARGIN, ITEM_MARGIN);
diff --git a/lib/thumbnailview/thumbnailbarview.cpp b/lib/thumbnailview/thumbnailbarview.cpp
--- a/lib/thumbnailview/thumbnailbarview.cpp
+++ b/lib/thumbnailview/thumbnailbarview.cpp
@@ -102,13 +102,15 @@
     {
         const QPoint shadowOffset(-SHADOW_SIZE, -SHADOW_SIZE + 1);
 
-        int key = rect.height() * 1000 + rect.width();
+        const auto dpr = painter->device()->devicePixelRatioF();
+        int key = qRound((rect.height() * 1000 + rect.width()) * dpr);
 
         ShadowCache::Iterator it = mShadowCache.find(key);
         if (it == mShadowCache.end()) {
             QSize size = QSize(rect.width() + 2 * SHADOW_SIZE, rect.height() + 2 * SHADOW_SIZE);
             QColor color(0, 0, 0, SHADOW_STRENGTH);
-            QPixmap shadow = PaintUtils::generateFuzzyRect(size, color, SHADOW_SIZE);
+            QPixmap shadow = PaintUtils::generateFuzzyRect(size * dpr, color, qRound(SHADOW_SIZE * dpr));
+            shadow.setDevicePixelRatio(dpr);
             it = mShadowCache.insert(key, shadow);
         }
         painter->drawPixmap(rect.topLeft() + shadowOffset, it.value());
@@ -175,7 +177,7 @@
         size = d->mView->gridSize();
     } else {
         QPixmap thumbnailPix = d->mView->thumbnailForIndex(index);
-        size = thumbnailPix.size();
+        size = thumbnailPix.size() / thumbnailPix.devicePixelRatio();
         size.rwidth() += ITEM_MARGIN * 2;
         size.rheight() += ITEM_MARGIN * 2;
     }
@@ -203,6 +205,7 @@
     bool isSelected = option.state & QStyle::State_Selected;
     bool isCurrent = d->mView->selectionModel()->currentIndex() == index;
     QPixmap thumbnailPix = d->mView->thumbnailForIndex(index);
+    QSize thumbnailSize = thumbnailPix.size() / thumbnailPix.devicePixelRatio();
     QRect rect = option.rect;
 
     QStyleOptionViewItem opt = option;
@@ -219,10 +222,10 @@
     // Draw thumbnail
     if (!thumbnailPix.isNull()) {
         QRect thumbnailRect = QRect(
-                                  rect.left() + (rect.width() - thumbnailPix.width()) / 2,
-                                  rect.top() + (rect.height() - thumbnailPix.height()) / 2 - 1,
-                                  thumbnailPix.width(),
-                                  thumbnailPix.height());
+                                  rect.left() + (rect.width() - thumbnailSize.width()) / 2,
+                                  rect.top() + (rect.height() - thumbnailSize.height()) / 2 - 1,
+                                  thumbnailSize.width(),
+                                  thumbnailSize.height());
 
         if (!thumbnailPix.hasAlphaChannel()) {
             d->drawShadow(painter, thumbnailRect);
diff --git a/lib/thumbnailview/thumbnailslider.cpp b/lib/thumbnailview/thumbnailslider.cpp
--- a/lib/thumbnailview/thumbnailslider.cpp
+++ b/lib/thumbnailview/thumbnailslider.cpp
@@ -65,7 +65,7 @@
 void ThumbnailSlider::updateToolTip()
 {
     // FIXME: i18n?
-    const int size = slider()->sliderPosition();
+    const int size = qRound(slider()->sliderPosition() * devicePixelRatioF());
     const QString text = QStringLiteral("%1 x %2").arg(size).arg(size);
     slider()->setToolTip(text);
 }
diff --git a/lib/thumbnailview/thumbnailview.cpp b/lib/thumbnailview/thumbnailview.cpp
--- a/lib/thumbnailview/thumbnailview.cpp
+++ b/lib/thumbnailview/thumbnailview.cpp
@@ -379,11 +379,12 @@
 {
     QSize value = d->mThumbnailSize;
     // mWaitingThumbnail
+    const auto dpr = devicePixelRatioF();
     int waitingThumbnailSize;
-    if (value.width() > 64) {
-        waitingThumbnailSize = 48;
+    if (value.width() > 64 * dpr) {
+        waitingThumbnailSize = qRound(48 * dpr);
     } else {
-        waitingThumbnailSize = 32;
+        waitingThumbnailSize = qRound(32 * dpr);
     }
     QPixmap icon = DesktopIcon(QStringLiteral("chronometer"), waitingThumbnailSize);
     QPixmap pix(value);
@@ -393,6 +394,7 @@
     painter.drawPixmap((value.width() - icon.width()) / 2, (value.height() - icon.height()) / 2, icon);
     painter.end();
     d->mWaitingThumbnail = pix;
+    d->mWaitingThumbnail.setDevicePixelRatio(dpr);
 
     // Stop smoothing
     d->mSmoothThumbnailTimer.stop();
@@ -406,21 +408,24 @@
         it.value().mAdjustedPix = QPixmap();
     }
 
-    emit thumbnailSizeChanged(value);
-    emit thumbnailWidthChanged(value.width());
+    emit thumbnailSizeChanged(value / dpr);
+    emit thumbnailWidthChanged(qRound(value.width() / dpr));
     if (d->mScaleMode != ScaleToFit) {
         scheduleDelayedItemsLayout();
     }
     d->scheduleThumbnailGeneration();
 }
 
 void ThumbnailView::setThumbnailWidth(int width)
 {
-    if(d->mThumbnailSize.width() == width) {
+    const auto dpr = devicePixelRatioF();
+    const qreal newWidthF = width * dpr;
+    const int newWidth = qRound(newWidthF);
+    if(d->mThumbnailSize.width() == newWidth) {
         return;
     }
-    int height = round((qreal)width / d->mThumbnailAspectRatio);
-    d->mThumbnailSize = QSize(width, height);
+    int height = qRound(newWidthF / d->mThumbnailAspectRatio);
+    d->mThumbnailSize = QSize(newWidth, height);
     updateThumbnailSize();
 }
 
@@ -443,7 +448,7 @@
 
 QSize ThumbnailView::thumbnailSize() const
 {
-    return d->mThumbnailSize;
+    return d->mThumbnailSize / devicePixelRatioF();
 }
 
 void ThumbnailView::setThumbnailViewHelper(AbstractThumbnailViewHelper* helper)
@@ -670,6 +675,7 @@
     if (fullSize) {
         *fullSize = thumbnail.mRealFullSize;
     }
+    thumbnail.mAdjustedPix.setDevicePixelRatio(devicePixelRatioF());
     return thumbnail.mAdjustedPix;
 }
 
@@ -810,7 +816,7 @@
     // setThumbnailSize() does not work
     //verticalScrollBar()->setSingleStep(d->mThumbnailSize / 5);
     if (event->modifiers() == Qt::ControlModifier) {
-        int width = d->mThumbnailSize.width() + (event->delta() > 0 ? 1 : -1) * WHEEL_ZOOM_MULTIPLIER;
+        int width = thumbnailSize().width() + (event->delta() > 0 ? 1 : -1) * WHEEL_ZOOM_MULTIPLIER;
         width = qMax(int(MinThumbnailSize), qMin(width, int(MaxThumbnailSize)));
         setThumbnailWidth(width);
     } else {