diff --git a/src/ui_scaling.py b/src/ui_scaling.py
index 8b156a7..71d2302 100644
--- a/src/ui_scaling.py
+++ b/src/ui_scaling.py
@@ -23,7 +23,8 @@ def get_scaling_factor(master):
             except:
                 # ... if that fails try the first one in the list
                 monitor = monitors[0]
-        dpi = monitor.width / (master.winfo_screenmmwidth() / 24.0)
+                
+        dpi = monitor.width / (monitor.width_mm / 24.0)
         scaling_factor = dpi / 72.0
     except BaseException as e:
         print("WARNING: could not calculate monitor dpi:", e)