diff --git a/src/apps/stylededit/Constants.h b/src/apps/stylededit/Constants.h
index b7a88f378b..a16940e7df 100644
--- a/src/apps/stylededit/Constants.h
+++ b/src/apps/stylededit/Constants.h
@@ -1,10 +1,11 @@
 /*
- * Copyright 2002-2010, Haiku, Inc. All Rights Reserved.
+ * Copyright 2002-2020, Haiku, Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
  *		Mattias Sundblad
  *		Andrew Bachmann
+ *		Pascal R. G. Abresch
  */
 #ifndef CONSTANTS_H
 #define CONSTANTS_H
@@ -53,6 +54,8 @@ const uint32 FONT_STYLE					= 'FSch';
 const uint32 FONT_COLOR					= 'Fcol';
 const uint32 kMsgSetItalic				= 'Fita';
 const uint32 kMsgSetBold				= 'Fbld';
+const uint32 kMsgSetFontDown				= 'Fsdw';
+const uint32 kMsgSetFontUp				= 'Fsup';
 
 const rgb_color palette[] = {
 	{ 220, 0, 0, 255 },		// red
@@ -93,5 +96,8 @@ const uint32 UPDATE_STATUS_REF			= 'UPSr';
 const uint32 UNLOCK_FILE				= 'UNLk';
 const uint32 UPDATE_LINE_SELECTION		= 'UPls';
 
+// fontSize constant
+const int32 fontSizes[] = {9, 10, 11, 12, 14, 18, 24, 36, 48, 72};
+
 #endif	// CONSTANTS_H
 
diff --git a/src/apps/stylededit/StyledEditWindow.cpp b/src/apps/stylededit/StyledEditWindow.cpp
index db7f5e0006..27e9ef3479 100644
--- a/src/apps/stylededit/StyledEditWindow.cpp
+++ b/src/apps/stylededit/StyledEditWindow.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012, Haiku, Inc. All Rights Reserved.
+ * Copyright 2002-2020, Haiku, Inc. All Rights Reserved.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -10,6 +10,7 @@
  *		Ryan Leavengood
  *		Vlad Slepukhin
  *		Sarzhuk Zharski
+ *		Pascal R. G. Abresch
  */
 
 
@@ -397,6 +398,42 @@ StyledEditWindow::MessageReceived(BMessage* message)
 			_SetFontStyle(fontFamily, fontStyle);
 			break;
 		}
+		case kMsgSetFontUp:
+		{
+			uint32 sameProperties;
+			BFont font;
+
+			fTextView->GetFontAndColor(&font, &sameProperties);
+			//GetFont seems to return a constant size for font.Size(),
+			//thus not used here (maybe that is a bug)
+			int32 cur_size = font.Size();
+
+			for (unsigned int a = 0;
+				a < sizeof(fontSizes)/sizeof(fontSizes[0]); a++) {
+				if (fontSizes[a] > cur_size) {
+					_SetFontSize(fontSizes[a]);
+					break;
+				}
+			}
+			break;
+		}
+		case kMsgSetFontDown:
+		{
+			uint32 sameProperties;
+			BFont font;
+
+			fTextView->GetFontAndColor(&font, &sameProperties);
+			int32 cur_size = font.Size();
+
+			for (unsigned int a = 1;
+				a < sizeof(fontSizes)/sizeof(fontSizes[0]); a++) {
+				if (fontSizes[a] >= cur_size) {
+					_SetFontSize(fontSizes[a-1]);
+					break;
+				}
+			}
+			break;
+		}
 		case kMsgSetItalic:
 		{
 			uint32 sameProperties;
@@ -1212,7 +1249,6 @@ StyledEditWindow::_InitWindow(uint32 encoding)
 	fFontSizeMenu->SetRadioMode(true);
 	fFontMenu->AddItem(fFontSizeMenu);
 
-	const int32 fontSizes[] = {9, 10, 11, 12, 14, 18, 24, 36, 48, 72};
 	for (uint32 i = 0; i < sizeof(fontSizes) / sizeof(fontSizes[0]); i++) {
 		BMessage* fontMessage = new BMessage(FONT_SIZE);
 		fontMessage->AddFloat("size", fontSizes[i]);
@@ -1234,6 +1270,15 @@ StyledEditWindow::_InitWindow(uint32 encoding)
 
 	fFontMenu->AddSeparatorItem();
 
+	BMenuItem* fontSizeUpItem = new BMenuItem(B_TRANSLATE("Increase size"),
+		new BMessage(kMsgSetFontUp));
+	BMenuItem* fontSizeDownItem = new BMenuItem(B_TRANSLATE("Decrease size"),
+		new BMessage(kMsgSetFontDown));
+	fFontMenu->AddItem(fontSizeUpItem);
+	fFontMenu->AddItem(fontSizeDownItem);
+	fontSizeUpItem->SetShortcut('+', 0);
+	fontSizeDownItem->SetShortcut('-', 0);
+
 	// "Bold" & "Italic" menu items
 	fFontMenu->AddItem(fBoldItem = new BMenuItem(B_TRANSLATE("Bold"),
 		new BMessage(kMsgSetBold)));