Height of string measured with MeasureString in PrintPreviewDialog differs from that in actual printing

private void button1_Click(object sender, EventArgs e)
    {
        Print();
    }

    public void Print()
    {
        PrintDocument my_doc = new PrintDocument();
        my_doc.PrintPage += new PrintPageEventHandler(this.PrintPage);

        PrintPreviewDialog my_preview = new PrintPreviewDialog();
        my_preview.Document = my_doc;

        my_preview.ShowDialog();

        my_doc.Dispose();
        my_preview.Dispose();
    }

    private void PrintPage(object sender,
       System.Drawing.Printing.PrintPageEventArgs e)
    {
        e.Graphics.PageUnit = GraphicsUnit.Pixel;

        string s = "String height is ";

        SizeF h = e.Graphics.MeasureString(s, new Font("Arial", 24));

        e.Graphics.DrawString(s + Convert.ToString(h.Height),
           new Font("Arial", 24), new SolidBrush(Color.Black), 1, 1);
    }

SizeF hT = TextRenderer.MeasureText(s, new Font("Arial", 24));