I want to move the content of a `RichTextBox` to a specific line of the content. The `RichTextBox` provides the method `ScrollToVerticalOffset` from the embedded `ScrollViewer`. The method is documented in MSDN, but the measurement unit of the parameter named offset is not [specified](http://msdn.microsoft.com/en-us/library/system.windows.controls.scrollviewer.scrolltoverticaloffset.aspx). The Type is `double`.

A [`VerticalOffset`](http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.textboxbase.verticaloffset.aspx) property of a `TextBox` is documented as in device-independent units (1/96th inch per unit).

So I tried to calculate the offset from the font size. The font size is given in pixels. The resulting formula is

```
offset = fontSize * 96 / 72  *  lineNumber;

```

But this jumps way behind the desired line. For now I am using this calculation:

```
offset = fontSize * lineNumber;

```

Is this correct?