'hier die APIs:
Private Declare Function GetDesktopWindow Lib "user32" () As Long
 
Private Declare Function GetDC Lib "user32" ( _
  ByVal hWnd As Long) As Long
 
Private Declare Function GetDeviceCaps Lib "gdi32" ( _
  ByVal hdc As Long, _
  ByVal nIndex As Long) As Long
 
Private Declare Function ReleaseDC Lib "user32" ( _
  ByVal hWnd As Long, _
  ByVal hdc As Long) As Long

Private Function DpiFaktor() As Single
Const LOGPIXELSX = 88
Dim hWndDesk&, hDCDesk&, logPix&, Proz&
 
    'DPI-Wert ermitteln: (z.B. logPix = 131)
    hWndDesk = GetDesktopWindow()
    hDCDesk = GetDC(hWndDesk)
    logPix = GetDeviceCaps(hDCDesk, LOGPIXELSX)
    Call ReleaseDC(hWndDesk, hDCDesk)
 
    'DPI-Wert in Prozent umrechnen:
    Proz& = (logPix * 100) / 96 '(z.B. Proz& = 136)
    'DPI-Wert als Faktor für Berechnung:
    DpiFaktor = Proz& / 100 '(z.B. 1.36)
 
End Function

DPI = DpiFaktor()
'ergibt z.B. 1.36 = 136%