Without using of a control or form:
using (System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(new Bitmap(1, 1)))
{
SizeF size = graphics.MeasureString("Hello there", new Font("Segoe UI", 11, FontStyle.Regular, GraphicsUnit.Point));
}
Or in VB.Net:
Using graphics As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(New Bitmap(1, 1))
Dim size As SizeF = graphics.MeasureString("Hello there", New Font("Segoe UI", 11, FontStyle.Regular, GraphicsUnit.Point))
End Using