The control limits are also called as the natural process limits, which has two parallel horizontal line called as upper & lower control limit. If the element in the chart is outside the limit, the process is out of control. The UCL & LCL find the variations of the plotted data in the chart. Find the lower and upper control limits using the control limit formula. The UCL LCL formula can be used to find if the signals are out of control in the process.