Now, let's move on to our yield. So the yield or the percent yield basically tells us how much of that protein that we essentially want to isolate we have left over compared to how much we begin with. So this describes the enzyme activity that is retained following each purification step and it is given as a percentage. Now, the equation for yield is the following. So it's the ratio of the enzyme activity of that specific procedure to the original enzyme activity found in that original sample that we begin with and we multiply the ratio by 100%. So because this is a ratio, the units cancel out and our units are simply percent.