Dim fontToMeasure As New Font("Microsoft Sans Serif", 14, FontStyle.Bold)
Dim sizeOfString As New SizeF
Dim g As Graphics = Me.CreateGraphics

sizeOfString = g.MeasureString("This is line 1" & vbcrlf & "This is line 2", fontToMeasure)
Debug.WriteLine("String Height: " & sizeOfString.Height)
Debug.WriteLine("String Width: " & sizeOfString.Width)

If you want to limit the width (so it wraps), use below (300 was my width to set as max):

Dim fontToMeasure As New Font("Microsoft Sans Serif", 14, FontStyle.Bold)
Dim sizeOfString As New SizeF
Dim g As Graphics = Me.CreateGraphics

sizeOfString = g.MeasureString("This is line 1" & vbcrlf & "This is line 2", fontToMeasure, 300)
Debug.WriteLine("String Height: " & sizeOfString.Height)
Debug.WriteLine("String Width: " & sizeOfString.Width)