diff --git a/CMakeLists.txt b/CMakeLists.txt
index dc49588..96b53d2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -55,6 +55,13 @@ file(GLOB_RECURSE SOURCES  "lv_drivers/*.c" "${InfiniTime_DIR}/src/libs/lvgl/src
 
 add_executable(infinisim main.cpp ${SOURCES} ${INCLUDES})
 
+set(MONITOR_ZOOM 1 CACHE STRING "Scale simulator window by this factor")
+if(MONITOR_ZOOM MATCHES "^[0-9]\.?[0-9]*")
+  target_compile_definitions(infinisim PRIVATE MONITOR_ZOOM=${MONITOR_ZOOM})
+else()
+  message(FATAL_ERROR "variable MONITOR_ZOOM=${MONITOR_ZOOM} must be a positive number")
+endif()
+
 # include the generated lv_conf.h file before anything else
 target_include_directories(infinisim PRIVATE "${CMAKE_CURRENT_BINARY_DIR}")
 
diff --git a/README.md b/README.md
index abfd7d5..9d1e469 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,7 @@ The following configuration settings can be added to the first `cmake -S . -B bu
 - `-DInfiniTime_DIR=InfiniTime`: a full path to an existing InfiniTime repository checked out.
   Inside that directory the `src/libs/lvgl` submodule must be checked out as well.
   The default value points to the InfiniTime submodule in this repository.
+- `-DMONITOR_ZOOM=1`: scale simulator window by this factor
 
 ## Run Simulator
 
diff --git a/lv_drv_conf.h b/lv_drv_conf.h
index 4a6e01f..f1e1111 100644
--- a/lv_drv_conf.h
+++ b/lv_drv_conf.h
@@ -99,7 +99,10 @@
 #  define MONITOR_VER_RES     240
 
 /* Scale window by this factor (useful when simulating small screens) */
+#ifndef MONITOR_ZOOM
 #  define MONITOR_ZOOM        1
+#endif
+static_assert(MONITOR_ZOOM > 0);
 
 /* Used to test true double buffering with only address changing.
  * Set LV_draw_buf_SIZE = (LV_HOR_RES * LV_VER_RES) and  LV_draw_buf_DOUBLE = 1 and LV_COLOR_DEPTH = 32" */
diff --git a/sim/drivers/Cst816s.cpp b/sim/drivers/Cst816s.cpp
index 6fae3ba..659511f 100644
--- a/sim/drivers/Cst816s.cpp
+++ b/sim/drivers/Cst816s.cpp
@@ -1,4 +1,5 @@
 #include "drivers/Cst816s.h"
+#include "lv_drv_conf.h" // MONITOR_ZOOM
 #include <SDL2/SDL.h>
 #include <libraries/log/nrf_log.h>
 #include <cmath>
@@ -25,6 +26,10 @@ bool Cst816S::Init() {
 Cst816S::TouchInfos Cst816S::GetTouchInfo() {
   int x, y;
   uint32_t buttons = SDL_GetMouseState(&x, &y);
+  // scale down real mouse coordinates to InfiniTime scale to make zoom work
+  // the MONITOR_ZOOM-factor is defined in lv_drv_conf.h
+  x /= MONITOR_ZOOM;
+  y /= MONITOR_ZOOM;
 
   Cst816S::TouchInfos info;
   info.x = x;