Try this.
int originalPictureWidth = 50;
int originalPictureHeight = 50;
double xScale = (double)pictureBox1.Width / (double)originalPictureWidth;
double yScale = (double)pictureBox1.Height / (double)originalPictureHeight;
using (DataSet ds = new LayoutDAL().GetLayoutDetails(_layoutId))
{
Button bt = new Button(); bt.SetBounds(
(int)(Convert.ToDouble(ds.Tables[0].Rows[i]["LocationX"]) * xScale),
(int)(Convert.ToDouble(ds.Tables[0].Rows[i]["LocationY"]) * yScale), 60, 60);
}