diff --git a/src/calibre/gui2/tweak_book/__init__.py b/src/calibre/gui2/tweak_book/__init__.py
index 0a49f381d7..1f24bc2d29 100644
--- a/src/calibre/gui2/tweak_book/__init__.py
+++ b/src/calibre/gui2/tweak_book/__init__.py
@@ -70,6 +70,7 @@ d['templates'] = {}
 d['auto_close_tags'] = True
 d['restore_book_state'] = True
 d['editor_accepts_drops'] = True
+d['toolbar_icon_size'] = 24
 del d
 
 ucase_map = {l:string.ascii_uppercase[i] for i, l in enumerate(string.ascii_lowercase)}
diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index a72b1c9deb..a6ba0ae644 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -148,6 +148,7 @@ class Boss(QObject):
 
     def preferences(self):
         orig_spell = tprefs['inline_spell_check']
+        orig_size = tprefs['toolbar_icon_size']
         p = Preferences(self.gui)
         ret = p.exec_()
         if p.dictionaries_changed:
@@ -158,6 +159,12 @@ class Boss(QObject):
             for ed in editors.itervalues():
                 if hasattr(ed, 'populate_toolbars'):
                     ed.populate_toolbars()
+        if orig_size != tprefs['toolbar_icon_size']:
+            for ed in editors.itervalues():
+                if hasattr(ed, 'bars'):
+                    for bar in ed.bars:
+                        bar.setIconSize(QSize(tprefs['toolbar_icon_size'], tprefs['toolbar_icon_size']))
+
         if ret == p.Accepted:
             setup_cssutils_serialization()
             self.gui.apply_settings()
diff --git a/src/calibre/gui2/tweak_book/editor/image.py b/src/calibre/gui2/tweak_book/editor/image.py
index a9d7f9356c..2d5ecd876a 100644
--- a/src/calibre/gui2/tweak_book/editor/image.py
+++ b/src/calibre/gui2/tweak_book/editor/image.py
@@ -10,7 +10,7 @@ import sys
 from functools import partial
 
 from PyQt5.Qt import (
-    QMainWindow, Qt, QApplication, pyqtSignal, QLabel, QIcon, QFormLayout,
+    QMainWindow, Qt, QApplication, pyqtSignal, QLabel, QIcon, QFormLayout, QSize,
     QDialog, QSpinBox, QCheckBox, QDialogButtonBox, QToolButton, QMenu, QInputDialog)
 
 from calibre.gui2 import error_dialog
@@ -284,6 +284,7 @@ class Editor(QMainWindow):
         for x in self.bars:
             x.setFloatable(False)
             x.topLevelChanged.connect(self.toolbar_floated)
+            x.setIconSize(QSize(tprefs['toolbar_icon_size'], tprefs['toolbar_icon_size']))
         self.restore_state()
 
     def toolbar_floated(self, floating):
diff --git a/src/calibre/gui2/tweak_book/editor/widget.py b/src/calibre/gui2/tweak_book/editor/widget.py
index ac22e2c601..2e4af3088d 100644
--- a/src/calibre/gui2/tweak_book/editor/widget.py
+++ b/src/calibre/gui2/tweak_book/editor/widget.py
@@ -11,7 +11,7 @@ from functools import partial
 
 from PyQt5.Qt import (
     QMainWindow, Qt, QApplication, pyqtSignal, QMenu, qDrawShadeRect, QPainter,
-    QImage, QColor, QIcon, QPixmap, QToolButton, QAction, QTextCursor)
+    QImage, QColor, QIcon, QPixmap, QToolButton, QAction, QTextCursor, QSize)
 
 from calibre import prints
 from calibre.constants import DEBUG
@@ -25,7 +25,8 @@ from calibre.gui2.tweak_book.editor.help import help_url
 from calibre.gui2.tweak_book.editor.text import TextEdit
 from calibre.utils.icu import utf16_length
 
-def create_icon(text, palette=None, sz=32, divider=2):
+def create_icon(text, palette=None, sz=None, divider=2):
+    sz = sz or tprefs['toolbar_icon_size']
     if palette is None:
         palette = QApplication.palette()
     img = QImage(sz, sz, QImage.Format_ARGB32)
@@ -34,7 +35,7 @@ def create_icon(text, palette=None, sz=32, divider=2):
     p.setRenderHints(p.TextAntialiasing | p.Antialiasing)
     qDrawShadeRect(p, img.rect(), palette, fill=QColor('#ffffff'), lineWidth=1, midLineWidth=1)
     f = p.font()
-    f.setFamily('Liberation Sans'), f.setPixelSize(sz // divider), f.setBold(True)
+    f.setFamily('Liberation Sans'), f.setPixelSize(int(sz // divider)), f.setBold(True)
     p.setFont(f), p.setPen(Qt.black)
     p.drawText(img.rect().adjusted(2, 2, -2, -2), Qt.AlignCenter, text)
     p.end()
@@ -301,6 +302,7 @@ class Editor(QMainWindow):
         for x in self.bars:
             x.setFloatable(False)
             x.topLevelChanged.connect(self.toolbar_floated)
+            x.setIconSize(QSize(tprefs['toolbar_icon_size'], tprefs['toolbar_icon_size']))
 
     def toolbar_floated(self, floating):
         if not floating:
diff --git a/src/calibre/gui2/tweak_book/preferences.py b/src/calibre/gui2/tweak_book/preferences.py
index 2cca72ca2b..cf2b479d9e 100644
--- a/src/calibre/gui2/tweak_book/preferences.py
+++ b/src/calibre/gui2/tweak_book/preferences.py
@@ -425,6 +425,14 @@ class ToolbarSettings(QWidget):
         self.toggle_visibility(False)
         self.bars.currentIndexChanged.connect(self.bar_changed)
 
+        self.toolbar_icon_size = ics = QSpinBox(self)
+        ics.setMinimum(16), ics.setMaximum(128), ics.setSuffix(' px'), ics.setValue(tprefs['toolbar_icon_size'])
+        ics.setToolTip('<p>' + _('Adjust the size of icons on all toolbars'))
+        r = l.rowCount()
+        self.toolbar_icon_size_label = la = QLabel(_('Toolbar &icon size:'))
+        la.setBuddy(ics)
+        l.addWidget(la, r, 0), l.addWidget(ics, r, 1)
+
     def read_settings(self, prefs=None):
         prefs = prefs or tprefs
         val = self.original_settings = {}
@@ -541,9 +549,12 @@ class ToolbarSettings(QWidget):
         self.read_settings(tprefs.defaults)
         self.original_settings = o
         self.build_lists()
+        self.toolbar_icon_size.setValue(tprefs.defaults['toolbar_icon_size'])
         self.changed_signal.emit()
 
     def commit(self):
+        if self.toolbar_icon_size.value() != tprefs['toolbar_icon_size']:
+            tprefs['toolbar_icon_size'] = self.toolbar_icon_size.value()
         if self.original_settings != self.current_settings:
             self.changed = True
             with tprefs:
diff --git a/src/calibre/gui2/tweak_book/ui.py b/src/calibre/gui2/tweak_book/ui.py
index 4c58240a0b..107de3cb61 100644
--- a/src/calibre/gui2/tweak_book/ui.py
+++ b/src/calibre/gui2/tweak_book/ui.py
@@ -14,7 +14,7 @@ from future_builtins import map
 from PyQt5.Qt import (
     QDockWidget, Qt, QLabel, QIcon, QAction, QApplication, QWidget, QEvent,
     QVBoxLayout, QStackedWidget, QTabWidget, QImage, QPixmap, pyqtSignal,
-    QMenu, QHBoxLayout, QTimer, QUrl)
+    QMenu, QHBoxLayout, QTimer, QUrl, QSize)
 
 from calibre import prints
 from calibre.constants import __appname__, get_version, isosx, DEBUG
@@ -289,6 +289,8 @@ class Main(MainWindow):
             self.setCorner(getattr(Qt, '%s%sCorner' % tuple(map(capitalize, (v, h)))), area)
         self.preview.apply_settings()
         self.live_css.apply_theme()
+        for bar in (self.global_bar, self.tools_bar, self.plugins_bar):
+            bar.setIconSize(QSize(tprefs['toolbar_icon_size'], tprefs['toolbar_icon_size']))
 
     def show_status_message(self, msg, timeout=5):
         self.status_bar.showMessage(msg, int(timeout*1000))
@@ -609,6 +611,7 @@ class Main(MainWindow):
             b = self.addToolBar(text)
             b.setObjectName(name)  # Needed for saveState
             actions[name] = b.toggleViewAction()
+            b.setIconSize(QSize(tprefs['toolbar_icon_size'], tprefs['toolbar_icon_size']))
             return b
         self.global_bar = create(_('Book tool bar'), 'global')
         self.tools_bar = create(_('Tools tool bar'), 'tools')