var cellRectangle = dataGridView1.GetCellDisplayRectangle(1, 1, true);
// Can create Points using the Rectangle if you want.
Console.WriteLine("Top Left     x:{0}t y:{1}", cellRectangle.Left, cellRectangle.Top);
Console.WriteLine("Bottom Right x:{0}t y:{1}", cellRectangle.Right, cellRectangle.Bottom);