public static class GraphicsExtensions
{
    public static void DrawStringInside(this Graphics graphics, Rectangle rect, Font font, Brush brush, string text)
    {
        var textSize = graphics.MeasureString(text, font);
        var state = graphics.Save();
        graphics.TranslateTransform(rect.Left, rect.Top);
        graphics.ScaleTransform(rect.Width / textSize.Width, rect.Height / textSize.Height);
        graphics.DrawString(text, font, brush, PointF.Empty);
        graphics.Restore(state);
    }
}